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? 2013 microchip technology inc. ds20005192b-page 1 mcp9844 features: 1mhz, 2-wire i 2 c? interface user-selectable measurement resolution: - +0.5c, +0.25c, +0.125c, +0.0625c user-programmable temperature limits: - temperature window limit - critical temperature limit user-programmable temperature alert output specified v dd range: 1.7v to 3.6v operating current: 100 a (typical) available package: 8-pin tdfn temperature sensor features: temperature-to-digital converter (c) sensor accuracy: - 0.2c/1c (typ./max.) ? +75c to +95c - 0.5c/2c (typ./max.) ? +40c to +125c - 1c/3c (typ./max.) ? -40c to +125c typical applications: temperature sensing for solid state drive (ssd) general purpose temperature datalog general purpose industrial applications industrial freezers and refrigerators food processing personal computers and servers pc peripherals consumer electronics handheld/portable devices description: microchip technology inc.s mcp9844 digital temperature sensor converts temperature from -40c to +125c to a digital word. it provides an accuracy of 0.2c/1c (typical/maximum) from +75c to +95c with an operating voltage of 1.7v to 3.6v. the mcp9844 digital temperature sensor comes with user-programmable registers that provide flexibility for temperature sensing applications. the registers allow user-selectable settings such as shutdown or low- power modes, and the specification of temperature event boundaries. when the temperature changes beyond the specified event boundary limits, the mcp9844 outputs an alert signal at the event pin. the user has the option of setting the temperature event output signal polarity as either an active-low or active- high comparator output for the thermostat operation, or as a temperature event interrupt output for microprocessor-based systems. this sensor has an industry standard i 2 c fast mode plus compatible 1 mhz serial interface. package types -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 -40 -20 0 20 40 60 80 100 120 temperature accuracy (c) t a (c) v dd = 1.7 v to 3.6 v 16 units spec. limits +std. dev. average -std. dev. 8-pin 2x3 tdfn * * includes exposed thermal pad (ep); see ta b l e 3 -1 . scl event sda a1a2 1 2 3 4 8 7 6 5 gnd a0 v dd ep 9 1 c accurate, 1.8v digital temperature sensor downloaded from: http:///
mcp9844 ds20005192b-page 2 ? 2013 microchip technology inc. 1.0 electrical characteristics absolute maximum ratings ? v dd .................................................................................. 4.0v voltage at all input/output pins ............... gnd C 0.3v to 4.0v pin a0....................................................... gnd C 0.3v to 11v storage temperature .....................................-65c to +150c ambient temp. with power applied ................-40c to +125c junction temperature (t j )...........................................+150c esd protection on all pins (hbm:mm) ................. (4 kv:200v) latch-up current at each pin (25c)........................ 200 ma ?notice: stresses above those listed under maximum ratings may cause permanent damage to the device. this is a stress rating only and functional operation of the device at those or any other conditions above those indicated in the operational listings of this sp ecification is not implied. exposure to maximum rating conditions for extended periods may affect device reliability. temperature sensor dc characteristics electrical specifications: unless otherwise indicated, v dd = 1.7v to 3.6v, gnd = ground, and t a = -40c to +125c. parameters sym. min. typ. max. unit conditions temperature sensor accuracy +75c < t a ? +95c t acy -1.0 0.2 +1.0 c v dd =1.8v +40c < t a ? +125c -2.0 0.5 +2.0 c -40c < t a ? +125c -3.0 1 +3.0 c temperature conversion time 0.5c/bit t conv 3 0 m s 0.25c/bit (por default) 65 125 ms 15 s/sec (typical) (see section 5.2.4 ) 0.125c/bit 130 ms 0.0625c/bit 260 ms power supply specified voltage range v dd 1.7 3.6 v operating current i dd 1 0 0 5 0 0 a shutdown current i shdn 0 . 2 1 at a = 85c power on reset (por) v por 1.4 1.6 v threshold for falling v dd voltage settling time after por t por 1 ms for warm and cold power cycles line regulation ? c 0.2 c v dd = 1.7v to 3.6v event output (open-drain output, external pull-up resistor required), see section 5.2.3 high-level current (leakage) i oh 1 av oh = v dd low-level voltage v ol 0 . 4 vi ol = 3 ma (active-low, pull-up resistor) thermal response, from +25c (air) to +125c (oil bath) tdfn-8 t res 0.7 s time to 63% (89c) downloaded from: http:///
? 2013 microchip technology inc. ds20005192b-page 3 mcp9844 input/output pin dc characteristics electrical specifications: unless otherwise indicated, v dd = 1.7v to 3.6v, gnd = ground and t a = -40c to +125c. parameters sym. min. typ. max. units conditions serial input/output (scl, sda, a0, a1, a2) input high-level voltage v ih 0.7v dd v low-level voltage v il 0 . 3 v dd v input current i in 5 a sda and scl only input impedance (a0, a1, a2) z in 1m ? v in > v ih input impedance (a0, a1, a2) z in 2 0 0k ? v in < v il output (sda only) low-level voltage v ol 0 . 4vi ol = 3 ma high-level current (leakage) i oh 1 a v oh = v dd low-level current i ol 20 ma v ol = 0.4v, v dd 2.2v 6m a v ol = 0.6v capacitance c in 5p f sda and scl inputs hysteresis v hyst 0 . 0 5 v dd v spike suppression t sp 50 ns temperature characteristics electrical specifications: unless otherwise indicated, v dd = 1.7v to 3.6v, gnd = ground, and t a = -40c to +125c. parameters sym. min. typ. max. units conditions temperature ranges specified temperature range t a -40 +125 c note 1 operating temperature range t a -40 +125 c storage temperature range t a -65 +150 c thermal package resistances thermal resistance, 8l-tdfn ? ja 5 2 . 5 c / w note 1: operation in this range must not cause t j to exceed maximum junction temperature (+150c). downloaded from: http:///
mcp9844 ds20005192b-page 4 ? 2013 microchip technology inc. timing diagram serial interface timing specifications electrical specifications: unless otherwise indicated, gnd = ground, t a = -40c to +125c, and c l = 80 pf note 1 . v dd = 1.7v to 3.6v v dd = 2.2v to 3.6v 100 khz 400 khz 1000 khz parameters sym. min. max. min. max. min. max. units 2-wire i 2 c? interface serial port frequency ( note 2 , 4 )f scl 10 100 10 400 10 1000 khz low clock ( note 2 )t low 4700 1300 500 ns high clock t high 4000 600 260 ns rise time ( note 5 )t r 1000 20 300 120 ns fall time ( note 5 )t f 20 300 20 300 120 ns data in setup time ( note 3 )t su:dat 250 100 5 0n s data in hold time ( note 6 )t hd:di 0 0 0n s data out hold time ( note 4 )t hd:do 200 900 200 900 0 350 ns start condition setup time t su:sta 4700 600 260 ns start condition hold time t hd:sta 4000 600 260 ns stop condition setup time t su:sto 4000 600 260 ns bus idle/free t b-free 4700 1300 500 ns time out t out 25 35 25 35 25 35 ms bus capacitive load c b 400 100 pf note 1: all values referred to v il max and v ih min levels. 2: if t low > t out , the temperature sensor i 2 c interface will time out. a repeat start command is required for communication. 3: this device can be used in a standard mode i 2 c bus system, but the requirement t su:dat ? 250 ns must be met. this device does not stretch scl low period. it outputs the next data bit to the sda line within t r max + t su:dat min = 1000 ns + 250 ns = 1250 ns (according to the standard mode i 2 c bus specification) before the scl line is released. 4: as a transmitter, the device provides internal minimum delay time t hd:dat min to bridge the undefined region (min. 200 ns) of the falling edge of scl t f max to avoid unintended generation of start or stop conditions. 5: characterized but not production tested. 6: as a receiver, sda should not be sampled at the falling edge of scl. sda can transition t hd:di 0 ns after scl toggles low. t s u:sto t su: d i t su:di t su:sto t b:fre e s cl sda t h d :d i / t hd : do t hi gh t l ow t ou t t r , t f start condition data transmission stop condition downloaded from: http:///
? 2013 microchip technology inc. ds20005192b-page 5 mcp9844 2.0 typical performance curves note: unless otherwise indicated, v dd = 1.7v to 3.6v, gnd = ground, sda/scl pulled-up to v dd , and t a = -40c to +125c. figure 2-1: temperature accuracy. figure 2-2: temperature accuracy histogram, t a = + 85 c. figure 2-3: temperature accuracy histogram, t a = + 25 c. figure 2-4: supply current vs. temperature. figure 2-5: shutdown current vs. temperature. figure 2-6: power-on reset threshold voltage vs. temperature. note: the graphs and tables provided following this note are a statistical summary based on a limited number of samples and are provided for informational purposes only. the performance characteristics listed herein are not tested or guaranteed. in some graphs or tables, the data presented may be outside the specified operating range (e.g., outside specified power supply range) and therefore outside the warranted range. -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 -40 -20 0 20 40 60 80 100 120 temperature accuracy (c) t a (c) v dd = 1.7 v to 3.6 v 16 units spec. limits +std. dev. average -std. dev. 25% 50% 75% 100% occurrences t a = +85 c v dd = 1.7 v - 3.6 v 16 units 0% -1.00-0.75 -0.50 -0.25 0.000.25 0.50 0.75 1.00 temperature accuracy (c) 25% 50% 75% 100% occurrences t a = +25 c v dd = 1.7 v - 3.6 v 16 units 0% -1.00-0.75 -0.50 -0.25 0.000.25 0.50 0.75 1.00 temperature accuracy (c) 75 100 125 150 i dd (a) 50 75 -40 -20 0 20 40 60 80 100 120 t a (c) 025 0.50 0.75 1.00 i shdn (a) 0.00 0 . 25 -40 -20 0 20 40 60 80 100 120 t a (c ) 1 1.2 1.4 1.6 1.8 v por (v) falling v dd rising v dd 0.6 0.8 -40 -20 0 20 40 60 80 100 120 t a (c) downloaded from: http:///
mcp9844 ds20005192b-page 6 ? 2013 microchip technology inc. note: unless otherwise indicated, v dd = 1.7v to 3.6v, gnd = ground, sda/scl pulled-up to v dd , and t a = -40c to +125c. figure 2-7: event output and sda v ol vs. temperature. figure 2-8: temperature conversion rate vs. temperature. figure 2-9: sda i ol vs. temperature. figure 2-10: line regulation: change in temperature accuracy vs. change in v dd . figure 2-11: i 2 c? protocol time-out vs. temperature. 01 0.2 0.3 0.4 e nt & sda v ol (v) sda, i ol = 20 ma v dd = 2.2 v to 3.6 v 0 0 . 1 -40 -20 0 20 40 60 80 100 120 ev e t a (c) event, i ol = 3 ma 50 75 100 125 150 175 200 t conv (ms) 0.0625 c/lsb 0.125 c/lsb 0 25 50 -40 -20 0 20 40 60 80 100 120 t a (c) 0.25 c/lsb 0.5 c/lsb 20 30 40 50 sda i ol (ma) v ol = 0.6v 10 20 -40 -20 0 20 40 60 80 100 120 t a (c) -1.0 0.0 1.0 2.0 3.0 l ized temp. error (c) v dd = 1.7 v v dd = 3.6 v -3.0 -2.0 -40 -20 0 20 40 60 80 100 120 norma l t a (c) 30 35 c bus t out (ms) 25 -40 -20 0 20 40 60 80 100 120 i 2 c t a (c) downloaded from: http:///
? 2013 microchip technology inc. ds20005192b-page 7 mcp9844 3.0 pin description the descriptions of the pins are listed in tab l e 3 - 1 . table 3-1: pin function tables 3.1 address pins (a0, a1, a2) these pins are device address input pins. the address pins correspond to the least significant bits (lsb) of the address bits. the most significant bits (msb) are a6, a5, a4, a3. refer to ta b l e 3 - 2 . all address pins have an internal pull-down resistor. 3.2 ground pin (gnd) the gnd pin is the system ground pin. 3.3 serial data line (sda) the sda is a bidirectional input/output pin used to serially transmit data to/from the host controller. this pin requires a pull-up resistor. (see section 4.0 ?serial communication? .) 3.4 serial clock line (scl) the scl is a clock input pin. all communication and timing is relative to the signal on this pin. the clock is generated by the host or master controller on the bus. (see section 4.0 ?serial communication? .) 3.5 temperature alert, open-drain output (event) the mcp9844 temperature event output pin is an open-drain output. the device outputs a signal when the ambient temperature goes beyond the user programmed temperature limit. (see section 5.2.3 ?event output configuration? .) 3.6 power pin (v dd ) v dd is the power pin. the operating voltage range, as specified in the dc electrical specification table, is applied on this pin. 3.7 exposed thermal pad (ep) there is an internal electrical connection between the exposed thermal pad (ep) and the gnd pin; they can be connected to the same potential on the printed circuit board (pcb). this provides better thermal conduction from the pcb to the die. mcp9844 symbol description tdfn 1 a0 slave address 2 a1 slave address 3 a2 slave address 4 gnd ground 5 sda serial data line 6 scl serial clock line 7 event temperature alert output 8v dd power pin 9 ep exposed thermal pad (ep); can be connected to gnd. table 3-2: mcp9844 address byte device address code slave address a6 a5 a4 a3 a2 a1 a0 sensor 0011x 1 x 1 x 1 note 1: user-selectable address is shown by x, where x is 1 or 0 for v dd and gnd, respectively downloaded from: http:///
mcp9844 ds20005192b-page 8 ? 2013 microchip technology inc. 4.0 serial communication 4.1 2-wire standard mode i 2 c? protocol-compatible interface the mcp9844 serial clock input (scl) and the bidirectional serial data line (sda) form a 2-wire bidirectional standard mode i 2 c compatible communication port (refer to the input/output pin dc characteristics table and the serial interface timing specifications table). the following mcp9844 bus protocol is defined in table 4-1 . table 4-1: mcp9844 serial bus protocol descriptions 4.1.1 data transfer data transfers are initiated by a start condition (start), followed by a 7-bit device address and a read/write bit. an acknowledge (ack) from the slave confirms the reception of each byte. each access must be terminated by a stop condition (stop). repeated communication is initiated after t b-free . this device does not support sequential register read/ write. each register needs to be addressed using the register pointer. this device supports the receive protocol. the register can be specified using the pointer for the initial read. each repeated read or receive begins with a start condition and address byte. the mcp9844 retains the previously selected register. therefore, they output data from the previously specified register (repeated pointer specification is not necessary). 4.1.2 master/slave the bus is controlled by a master device (typically a microcontroller) that controls the bus access and generates the start and stop conditions. the mcp9844 is a slave device and does not control other devices in the bus. both master and slave devices can operate as either transmitter or receiver. however, the master device determines which mode is activated. 4.1.3 start/stop condition a high-to-low transition of the sda line (while scl is high) is the start condition. all data transfers must be preceded by a start condition from the master. a low- to-high transition of the sda line (while scl is high) signifies a stop condition. if a start or stop condition is introduced during data transmission, the mcp9844 releases the bus. all data transfers are ended by a stop condition from the master. 4.1.4 address byte following the start condition, the host must transmit an 8-bit address byte to the mcp9844. the address for the mcp9844 temperature sensor is 0011,a2,a1,a0 in binary, where the a2, a1 and a0 bits are set externally by connecting the corresponding pins to v dd 1 or gnd 0 . the 7-bit address transmitted in the serial bit stream must match the selected address for the mcp9844 to respond with an ack. bit 8 in the address byte is a read/write bit. setting this bit to 1 commands a read operation, while 0 commands a write operation (see figure 4-1 ). figure 4-1: device addressing. term description master the device that controls the serial bus, typically a microcontroller. slave the device addressed by the master, such as the mcp9844. transmitter device sending data to the bus. receiver device receiving data from the bus. start a unique signal from the master to initiate serial interface with a slave. stop a unique signal from the master to terminate serial interface from a slave. read/write a read or write to the mcp9844 registers. ack a receiver acknowledges (ack) the reception of each byte by polling the bus. nak a receiver not-acknowledges (nak) or releases the bus to show end-of-data (eod). busy communication is not possible because the bus is in use. not busy the bus is in the idle state, both sda and scl remain high. data valid sda must remain stable before scl becomes high in order for a data bit to be considered valid. during normal data transfers, sda only changes state while scl is low. 123456789 scl sda 00 11 a2 a1 a0 start address byte slave address r/w mcp9844 response code address ac k downloaded from: http:///
? 2013 microchip technology inc. ds20005192b-page 9 mcp9844 4.1.5 data valid after the start condition, each bit of data in the transmission needs to be settled for a time specified by t su-data before scl toggles from low-to-high (see serial interface timing specifications table). 4.1.6 acknowledge (ack/nak) each receiving device, when addressed, is obliged to generate an ack bit after the reception of each byte. the master device must generate an extra clock pulse for ack to be recognized. the acknowledging device pulls down the sda line for t su-data before the low-to-high transition of scl from the master. sda also needs to remain pulled down for t h-data after a high-to-low transition of scl. during read, the master must signal an end-of-data (eod) to the slave by not generating an ack bit (nak) once the last bit has been clocked out of the slave. in this case, the slave will leave the data line released to enable the master to generate the stop condition. 4.1.7 time out (t out ) if the scl stays low or high for time specified by t out , the mcp9844 resets the serial interface. this dictates the minimum clock speed as specified in the specification. downloaded from: http:///
mcp9844 ds20005192b-page 10 ? 2013 microchip technology inc. 5.0 functional description the mcp9844 temperature sensors consist of a band gap type temperature sensor, a delta-sigma analog-to- digital converter ( ??? adc), user-programmable registers and a 2-wire i 2 c protocol compatible serial interface. figure 5-1 shows a block diagram of the register structure. figure 5-1: functional block diagram. clear event 0.5c/bit 0.25c/bit 0.125c/bit 0.0625c/bit temperature t upper t lower configuration ?? adc band gap temperature sensor event status output control critical event only event polarity event comp./int. t crit capability temp. range accuracy output feature register pointer critical trip lock alarm win. lock bit shutdown hysteresis manufacturer id resolution device id/rev. selected resolution standard i 2 c interface a0 a1 a2 event sda scl v dd gnd i 2 c? bus time-out shutdown status mcp9844 temperature sensor downloaded from: http:///
? 2013 microchip technology inc. ds20005192b-page 11 mcp9844 5.1 registers the mcp9844 device has several registers that are user accessible. these registers include the capability register, configuration register, event temperature upper-boundary and lower-boundary trip registers, critical temperature trip register, temperature register, manufacturer identification register and device identification register. the temperature register is read-only and is used to access the ambient temperature data. the data is loaded in parallel to this register after t conv . the event temperature upper-boundary and lower-boundary trip registers are read/writes. if the ambient temperature drifts beyond the user-specified limits, the mcp9844 device outputs a signal using the event pin (refer to section 5.2.3 ?event output configuration? ). in addition, the critical temperature trip register is used to provide an additional critical temperature limit. the capability register is used to provide bits describing the mcp9844s capability in measurement resolution, measurement range and device accuracy. the device configuration register provides access to configure the mcp9844s various features. these registers are described in further detail in the following sections. the registers are accessed by sending a register pointer to the mcp9844 using the serial interface. this is an 8-bit write-only pointer. register 5-1 describes the pointer or the address of each register. this device will not acknowledge commands to register pointers other than those listed in register 5-1. register 5-1: register pointer (write only) w-0 w-0 w-0 w-0 w-0 w-0 w-0 w-0 pointer bits bit 7 bit 0 legend: r = readable bit w = writable bit u = unimplemented bit, read as 0 -n = value at por 1 = bit is set 0 = bit is cleared x = bit is unknown bit 7-4 writable bits: write 0 bit 3-0 pointer bits: 0000 = capability register 0001 = configuration register (config) 0010 = event temperature upper-boundary trip register (t upper ) 0011 = event temperature lower-boundary trip register (t lower ) 0100 = critical temperature trip register (t crit ) 0101 = temperature register (t a ) 0110 = manufacturer id register 0111 = device id/revision register 1000 = reserved 1001 = resolution register 1xxx = unused (the device will not acknowledge commands to other pointer locations.) downloaded from: http:///
mcp9844 ds20005192b-page 12 ? 2013 microchip technology inc. table 5-1: bit assignment summary for all temperature sensor registers (see section 5.3 ) register pointer (hex) msb/ lsb bit assignment 7654 3 2 10 0x00 msb 0000 0 0 00 lsb shdn status t out range 1 resolution range accuracy event 0x01 msb 0000 0 hysteresis shdn lsb crt. loc. win. loc. int. clr. evt. stat. evt. cnt. evt. sel. evt. pol. evt. mod. 0x02 msb 000 sign 2 7 c 2 6 c 2 5 c 2 4 c lsb 2 3 c 2 2 c 2 1 c 2 0 c 2 -1 c 2 -2 c 00 0x03 msb 000 sign 2 7 c 2 6 c 2 5 c 2 4 c lsb 2 3 c 2 2 c 2 1 c 2 0 c 2 -1 c 2 -2 c 00 0x04 msb 000 sign 2 7 c 2 6 c 2 5 c 2 4 c lsb 2 3 c 2 2 c 2 1 c 2 0 c 2 -1 c 2 -2 c 00 0x05 msb t a ?? t crit t a ?? t upper t a ?? t lower sign 2 7 c 2 6 c 2 5 c 2 4 c lsb 2 3 c 2 2 c 2 1 c 2 0 c 2 -1 c 2 -2 c 2 -3 c 2 -4 c 0x06 msb 0000 0 0 00 lsb 0101 0 1 00 0x07 msb 0000 0 1 10 lsb 0000 0 0 01 0x08 msb 0000 0 1 10 lsb 0000 0 0 01 0x09 msb 0000 0 0 00 lsb 0000 0 0 resolution downloaded from: http:///
? 2013 microchip technology inc. ds20005192b-page 13 mcp9844 5.1.1 capability register this is a read-only register used to identify the temperature sensor capability. for example, the mcp9844 device is capable of providing temperature at 0.25c resolution, measuring temperature below and above 0c, providing 1c and 2c accuracy over the active and monitor temperature ranges (respectively) and providing user-programmable temperature event boundary trip limits. register 5-2 describes the capability register. these functions are described in further detail in the following sections. register 5-2: capability register (read-only) ? address ?0000 0000?b u-0 u-0 u-0 u-0 u-0 u-0 u-0 u-0 bit 15 bit 8 r-1 r-1 r-1 r-0 r-1 r-1 r-1 r-1 shdn status t out range resolution meas. range accuracy temp. alarm bit 7 bit 0 legend: r = readable bit w = writable bit u = unimplemented bit, read as 0 -n = value at por 1 = bit is set 0 = bit is cleared x = bit is unknown bit 15-8 unimplemented: read as 0 bit 7 event output status during shutdown (shdn status): 0 = event output remains in previous state. if the output asserts before shutdown command, it remains asserted during shutdown. 1 = event output deasserts during shutdown. after shutdown, it takes t conv to reassert the event output (power-up default) bit 6 i 2 c? bus time-out (t out range): 0 = bus time-out range is 10 ms to 60 ms 1 = bus time-out range is 25 ms to 35 ms (power-up default) bit 5 unimplemented: read as 1 bit 4-3 resolution: 00 = 0.5c 01 = 0.25c (power-up default) 10 = 0.125c 11 = 0.0625c these bits reflect the selected resolution (see section 5.2.4 ?temperature resolution? ) bit 2 temperature measurement range (meas. range): 0 =t a ?? 0 (decimal) for temperature below 0c ? 1 = the part can measure temperature below 0c (power-up default) downloaded from: http:///
mcp9844 ds20005192b-page 14 ? 2013 microchip technology inc. figure 5-2: timing diagram for reading the capability register (see section 4.0 ?serial communication? ). bit 1 accuracy: 0 =accuracy ?? 2c from +75c to +95c (active range) and 3c from +40c to +125c (monitor range) 1 =accuracy ?? 1c from +75c to +95c (active range) and 2c from +40c to +125c (monitor range) bit 0 temperature alarm: 0 = no defined function (this bit will never be cleared or set to 0 ) 1 = the part has temperature boundary trip limits (t upper /t lower /t crit registers) and a temperature event output (jc 42.4 required feature) register 5-2: capability register (read-only) ? address ?0000 0000?b (continued) sda ac k 0011 a capability pointer 0000 ac k s 2 a 1 a 0 12345678 12345678 scl 0 address byte ac k 0011 a msb data ac k na k s p 2 a 1 a 0 12345678 12345678 12345678 address byte lsb data r mcp9844 mcp9844 mcp9844 master master w sda scl 000 00000 000 00001 111 downloaded from: http:///
? 2013 microchip technology inc. ds20005192b-page 15 mcp9844 5.1.2 sensor configuration register (config) the mcp9844 device has a 16-bit configuration register (config) that allows the user to set various functions for a robust temperature monitoring system. bits 10 through 0 are used to select the event output boundary hysteresis, device shutdown or low-power mode, temperature boundary and critical temperature lock, and temperature event output enable/disable. in addition, the user can select the event output condition (output set for t upper and t lower temperature boundary or t crit only), read event output status and set event output polarity and mode (comparator output or interrupt output mode). the temperature hysteresis bits 10 and 9 can be used to prevent output chatter when the ambient temperature gradually changes beyond the user specified temperature boundary (see section 5.2.2 ?temperature hysteresis (t hyst )? ). the continuous conversion or shutdown mode is selected using bit 8. in shutdown mode, the band gap temperature sensor circuit stops converting temperature and the ambient temperature register (t a ) holds the previous successfully converted temperature data (see section 5.2.1 ?shutdown mode? ). bits 7 and 6 are used to lock the user-specified boundaries t upper , t lower and t crit to prevent an accidental rewrite. bits 5 through 0 are used to configure the temperature event output pin. all functions are described in register 5-3 (see section 5.2.3 ?event output configuration? ). register 5-3: co nfiguration register (config) ? address 0000 0001b u-0 u-0 u-0 u-0 u-0 r/w-0 r/w-0 r/w-0 t hyst shdn bit 15 bit 8 r/w-0 r/w-0 r/w-0 r-0 r/w-0 r/w-0 r/w-0 r/w-0 crit. lock win. lock int. clear event stat. event cnt. event sel. event pol. event mod. bit 7 bit 0 legend: r = readable bit w = writable bit u = unimplemented bit, read as 0 -n = value at por 1 = bit is set 0 = bit is cleared x = bit is unknown bit 15-11 unimplemented: read as 0 bit 10-9 t upper and t lower limit hysteresis (t hyst ): 00 = 0c (power-up default) 01 = 1.5c 10 = 3.0c 11 = 6.0c (refer to section 5.2.3 ?event output configuration? ) this bit can not be altered when either of the lock bits are set (bit 6 and bit 7). this bit can be programmed in shutdown mode. bit 8 shutdown mode (shdn): 0 = continuous conversion (power-up default) 1 = shutdown (low-power mode) in shutdown, all power-consuming activities are disabled, though all registers can be written to or read. event output will deassert. this bit cannot be set 1 when either of the lock bits is set (bit 6 and bit 7). however, it can be cleared 0 for continuous conversion while locked (refer to section 5.2.1 ?shutdown mode? ). downloaded from: http:///
mcp9844 ds20005192b-page 16 ? 2013 microchip technology inc. bit 7 t crit lock bit (crit. lock): 0 = unlocked. t crit register can be written. (power-up default) 1 =locked. t crit register can not be written when enabled, this bit remains set 1 or locked until cleared by internal reset ( section 5.3 ?summary of power-on default? ). this bit does not require a double-write. this bit can be programmed in shutdown mode. bit 6 t upper and t lower window lock bit (win. lock): 0 = unlocked. t upper and t lower registers can be written. (power-up default) 1 =locked. t upper and t lower registers can not be written when enabled, this bit remains set 1 or locked until cleared by power-on respell ( section 5.3 ?sum- mary of power-on default? ). this bit does not require a double-write. this bit can be programmed in shutdown mode. bit 5 interrupt clear (int. clear) bit: 0 = no effect (power-up default) 1 = clear interrupt output. when read this bit returns 0 this bit clears the interrupt flag which deasserts event output. in shutdown mode, the event output is always deasserted. therefore, setting this bit in shutdown mode clears the interrupt after the device returns to normal operation. bit 4 event output status (event stat.) bit: 0 = event output is not asserted by the device (power-up default) 1 = event output is asserted as a comparator/interrupt or critical temperature output in shutdown mode this bit will clear because event output is always deasserted in shutdown m ode. bit 3 event output control (event cnt.) bit: 0 = event output disabled (power-up default) 1 = event output enabled this bit can not be altered when either of the lock bits is set (bit 6 and bit 7). this bit can be programmed in shutdown mode, but event output will remain deasserted. bit 2 event output select (event sel.) bit: 0 = event output for t upper , t lower and t crit (power-up default) 1 = t a t crit only. (t upper and t lower temperature boundaries are disabled.) when the alarm window lock bit is set, this bit cannot be altered until unlocked (bit 6). this bit can be programmed in shutdown mode, but event output will remain deasserted. bit 1 event output polarity (event pol.) bit: 0 = active-low (power-up default. pull-up resistor required) 1 = active-high this bit cannot be altered when either of the lock bits is set (bit 6 and bit 7). this bit can be programmed in shutdown mode, but event output will remain deasserted, see section 5.2.3 ?event output configuration? bit 0 event output mode (event mod.) bit: 0 = comparator output (power-up default) 1 = interrupt output this bit cannot be altered when either of the lock bits is set (bit 6 and bit 7). this bit can be programmed in shutdown mode, but event output will remain deasserted. register 5-3: co nfiguration register (config) ? address 0000 0001b downloaded from: http:///
? 2013 microchip technology inc. ds20005192b-page 17 mcp9844 figure 5-3: timing diagram for writing to the configuration register (see section 4.0 ?serial communication? . writing to the config register to enable the event output pin <0000 0000 0000 1000>b. sda ac k 0011 a 0000 ac k s 2 a 1 a 0 12345678 12345678 scl 0 address byte w mcp9844 mcp9844 msb data ac k ac k p 12345678 12345678 lsb data configuration pointer mcp9844 mcp9844 001 00000 000 00001 000 note: this is an example routine: i2c_start(); // send start command i2c_write(addressbyte & 0xfe); //write command //also, make sure bit 0 is cleared 0 i2c_write(0x01); // write config register i2c_write(0x00); // write data i2c_write(0x08); // write data i2c_stop(); // send stop command downloaded from: http:///
mcp9844 ds20005192b-page 18 ? 2013 microchip technology inc. figure 5-4: timing diagram for reading from the configuration register (see section 4.0 ?serial communication? ). sda ac k 0011 a configuration pointer 0000 ac k s 2 a 1 a 0 12345678 12345678 scl 0 address byte ac k 0011 a msb data ac k na k s p 2 a 1 a 0 12345678 12345678 12345678 address byte lsb data r mcp9844 mcp9844 mcp9844 master master w sda scl 001 00000 000 00001 000 reading the config register. note: it is not necessary to select the register pointer if it was set from the previous read/ write. note: this is an example routine: i2c_start(); // send start command i2c_write(addressbyte & 0xfe); //write command //also, make sure bit 0 is cleared 0 i2c_write(0x01); // write config register i2c_start(); // send repeat start command i2c_write(addressbyte | 0x01); //read command //also, make sure bit 0 is set 1 upperbyte = i2c_read(ack); // read 8 bits //and send ack bit lowerbyte = i2c_read(nak); // read 8 bits //and send nak bit i2c_stop(); // send stop command downloaded from: http:///
? 2013 microchip technology inc. ds20005192b-page 19 mcp9844 5.1.3 upper/lower/critical temperature limit registers (t upper /t lower /t crit ) the mcp9844 device has a 16-bit read/write event output temperature upper-boundary trip register (t upper ), a 16-bit lower-boundary trip register (t lower ) and a 16-bit critical boundary trip register (t crit ) that contains 11-bit data in twos complement format (0.25c). this data represents the maximum and minimum temperature boundary or temperature window that can be used to monitor ambient temperature. if this feature is enabled ( section 5.1.2 ?sensor configuration register (config)? ) and the ambient temperature exceeds the specified boundary or window, the mcp9844 asserts an event output. (refer to section 5.2.3 ?event output configuration? ). register 5-4: upper/lower/critical temperature limit register (t upper /t lower / t crit ) ? address 0000 0010b/0000 0011b / 0000 0100b ( note 1 ) u-0 u-0 u-0 r/w-0 r/w-0 r/w-0 r/w-0 r/w-0 s i g n2 7 c 2 6 c 2 5 c 2 4 c bit 15 bit 8 r/w-0 r/w-0 r/w-0 r/w-0 r/w-0 r/w-0 u-0 u-0 2 3 c 2 2 c 2 1 c 2 0 c 2 -1 c 2 -2 c bit 7 bit 0 legend: r = readable bit w = writable bit u = unimplemented bit, read as 0 -n = value at por 1 = bit is set 0 = bit is cleared x = bit is unknown bit 15-13 unimplemented: read as 0 bit 12 sign: 0 =t a ?? 0c ? 1 =t a ? 0c bit 11-2 t upper /t lower /t crit : temperature boundary trip data in twos complement format. bit 1-0 unimplemented: read as 0 note 1: this table shows two 16-bit registers for t upper , t lower and t crit located at 0000 0010b , 0000 0011b and 0000 0100b , respectively. downloaded from: http:///
mcp9844 ds20005192b-page 20 ? 2013 microchip technology inc. figure 5-5: timing diagram for writing and reading from the t upper register (see section 4.0 ?serial communication? ). sda ac k 0011 a t upper pointer 0000 ac k s 2 a 1 a 0 12345678 12345678 scl 0 address byte ac k 0011 a msb data ac k na k s p 2 a 1 a 0 12345678 12345678 12345678 address byte lsb data r mcp9844 mcp9844 mcp9844 master master w sda scl 010 00000 101 10100 000 reading from the t upper register. writing 90c to the t upper register <0000 0101 1010 0000>b. sda ac k 0011 a 0000 ac k s 2 a 1 a 0 12345678 12345678 scl 0 address byte w mcp9844 mcp9844 msb data ac k ac k p 12345678 12345678 lsb data t upper pointer mcp9844 mcp9844 010 00000 101 10100 000 note: it is not necessary to select the register pointer if it was set from the previous read/write. downloaded from: http:///
? 2013 microchip technology inc. ds20005192b-page 21 mcp9844 5.1.4 ambient temperature register (t a ) the mcp9844 device uses a band gap temperature sensor circuit to output analog voltage proportional to absolute temperature. an internal ?? adc is used to convert the analog voltage to a digital word. the con- verter resolution is set to 0.25c + sign (11-bit data). the digital word is loaded to a 16-bit read-only ambient temperature register (t a ) that contains 11-bit temperature data in twos complement format. the t a register bits (bits 12 through 0) are double-buff- ered. therefore, the user can access the register while, in the background, the mcp9844 performs an analog- to-digital conversion. the temperature data from the ?? adc is loaded in parallel to the t a register at t conv refresh rate. in addition, the t a register uses three bits (bits 15, 14 and 13) to reflect the event pin state. this allows the user to identify the cause of the event output trigger (see section 5.2.3 ?event output configuration? ); bit 15 is set to 1 if t a is greater than or equal to t crit , bit 14 is set to 1 if t a is greater than t upper and bit 13 is set to 1 if t a is less than t lower . the t a register bit assignment and boundary conditions are described in register 5-5 . register 5-5: ambient temperature register (t a ) ? address 0000 0101b ( note 1 ) r-0 r-0 r-0 r-0 r-0 r-0 r-0 r-0 t a vs. t crit t a vs. t upper t a vs. t lower sign 2 7 c 2 6 c 2 5 c 2 4 c bit 15 bit 8 r-0 r-0 r-0 r-0 r-0 r-0 r-0 r-0 2 3 c 2 2 c 2 1 c 2 0 c 2 -1 c 2 -2 c 2 -3 c 2 -4 c bit 7 bit 0 legend: r = readable bit w = writable bit u = unimplemented bit, read as 0 -n = value at por 1 = bit is set 0 = bit is cleared x = bit is unknown bit 15 t a vs. t crit (1) bit: 0 =t a ?? t crit 1 =t a ?? t crit bit 14 t a vs. t upper (1) bit: 0 =t a ?? t upper 1 =t a ?? t upper bit 13 t a vs. t lower (1) bit: 0 =t a ?? t lower 1 =t a ?? t lower bit 12 sign bit: 0 =t a ?? 0c ? 1 =t a ? 0c bit 11-0 ambient temperature (t a ) bits: ( note 2 ) 12-bit ambient temperature data in twos complement format. note 1: bits 15, 14 and 13 are not affected by the status of the event output configuration (bits 5 to 0 of c onfig) ( register 5-3 ). 2: bits 2, 1, and 0 may remain clear 0 depending on the status of the resolution register. the power-up default is 0.25c/bit, bits 1 and 0 remain clear 0 . downloaded from: http:///
mcp9844 ds20005192b-page 22 ? 2013 microchip technology inc. 5.1.4.1 t a bits to temperature conversion to convert the t a bits to decimal temperature, the upper three boundary bits 15, 14 and 13) must be masked out. then determine the sign bit (bit 12) to check positive or negative temperature, shift the bits accordingly and combine the upper and lower bytes of the 16-bit register. the upper byte contains data for temperatures greater than 32c while the lower byte contains data for temperature less than 32c, including fractional data. when combining the upper and lower bytes, the upper byte must be right-shifted by 4 bits (or multiply by 2 4 ), and the lower byte must be left-shifted by 4 bits (or multiply by 2 -4 ). adding the results of the shifted values provides the temperature data in decimal format, see equation 5-1 . the temperature bits are in twos compliment format; therefore, positive temperature data and negative tem- perature data are computed differently. equation 5-1 shows the temperature computation. the example instruction code outlined in figure 5-6 shows the communication flow. additionally, refer to figure 5-7 for the timing diagram. equation 5-1: bytes to temperature conversion figure 5-6: example instruction code. where: t a = ambient temperature (c) upperbyte = t a bit 15 to bit 8 lowerbyte = t a bit 7 to bit 0 temperature ? 0c temperature ? 0c t a upperbyte 2 4 lowerbyte 2 4 ? ? + ? ?? = t a upperbyte 2 4 lowerbyte 2 4 ? ? + ? ?? 256 ? = i2c_start(); // send start command i2c_write(addressbyte & 0xfe); //write command //also, make sure bit 0 is cleared 0 i2c_write(0x05); // write t a register address i2c_start(); //repeat start i2c_write(addressbyte | 0x01); // read command //also, make sure bit 0 is set 1 upperbyte = i2c_read(ack); // read 8 bits //and send ack bit lowerbyte = i2c_read(nak); // read 8 bits //and send nak bit i2c_stop(); // send stop command //convert the temperature data //first check flag bits if ((upperbyte & 0x80) == 0x80){ //t a ?? t crit } if ((upperbyte & 0x40) == 0x40){ //t a ?? t upper } if ((upperbyte & 0x20) == 0x20){ //t a ?? t lower } upperbyte = upperbyte & 0x1f; //clear flag bits if ((upperbyte & 0x10) == 0x10){ //t a ? 0c upperbyte = upperbyte & 0x0f; //clear sign temperature = (upperbyte x 16 + lowerbyte / 16) - 256; }else //t a ? 0c temperature = (upperbyte x 16 + lowerbyte / 16); // temperature = ambient temperature (c) this example routine assumes the variables and i 2 c? communication subroutines are predefined: downloaded from: http:///
? 2013 microchip technology inc. ds20005192b-page 23 mcp9844 figure 5-7: timing diagram for reading +25.25c temperature from the t a register (see section 4.0 ?serial communication? ). sda ac k 0011 a t a pointer 0000 ac k s 2 a 1 a 0 12345678 12345678 scl 0 address byte ac k 0011 a msb data ac k na k s p 2 a 1 a 0 12345678 12345678 12345678 address byte lsb data r mcp9844 mcp9844 mcp9844 master master w sda scl 101 00000 001 10010 100 note: it is not necessary to select the register pointer if it was set from the previous read/ write. downloaded from: http:///
mcp9844 ds20005192b-page 24 ? 2013 microchip technology inc. 5.1.5 manufacturer id register this register is used to identify the manufacturer of the device in order to perform manufacturer specific operations. the manufacturer id for the mcp9844 is 0x0054 (hexadecimal). figure 5-8: timing diagram for reading the manufacturer id register (see section 4.0 ?serial communication? ). register 5-6: manufacturer id register (read-only) ? address 0000 0110b r-0 r-0 r-0 r-0 r-0 r-0 r-0 r-0 manufacturer id bit 15 bit 8 r-0 r-1 r-0 r-1 r-0 r-1 r-0 r-0 manufacturer id bit 7 bit 0 legend: r = readable bit w = writable bit u = unimplemented bit, read as 0 -n = value at por 1 = bit is set 0 = bit is cleared x = bit is unknown bit 15-0 device manufacturer identification number . sda ac k 0011 a manuf. id pointer 0000 ac k s 2 a 1 a 0 12345678 12345678 scl 0 address byte ac k 0011 a msb data ac k na k s p 2 a 1 a 0 12345678 12345678 12345678 address byte lsb data r mcp9844 mcp9844 mcp9844 master master w sda scl 110 00000 000 01010 100 note: it is not necessary to select the register pointer if it was set from the previous read/ write. downloaded from: http:///
? 2013 microchip technology inc. ds20005192b-page 25 mcp9844 5.1.6 device id and revision register the device id and revision register located at address pointer 0x08 is used to identify microchip devices. the upper byte of these registers is used to specify the device identification and the lower byte is used to specify device silicon revision. the device id for the mcp9844 is 0x06 (hex). the revision (lower byte) begins with 0x00 (hex) for the first release, with the number being incremented as revised versions are released. register 5-7: tse2004av device id and device revision (read-only) ? address 0000 0111b and 0000 1000b r-0 r-0 r-0 r-0 r-0 r-1 r-1 r-0 device id bit 15 bit 8 r-0 r-0 r-0 r-0 r-0 r-0 r-0 r-1 device revision bit 7 bit 0 legend: r = readable bit w = writable bit u = unimplemented bit, read as 0 -n = value at por 1 = bit is set 0 = bit is cleared x = bit is unknown bit 15-8 device id: bit 15 to bit 8 are used for device id bit 7-0 device revision: bit 7 to bit 0 are used for device revision downloaded from: http:///
mcp9844 ds20005192b-page 26 ? 2013 microchip technology inc. 5.1.7 resolution register this register allows the user to change the sensor resolution (see section 5.2.4 ?temperature resolution? ). the por default resolution is 0.25c. the selected resolution is also reflected in the capability register (see register 5-2 ). note: in order to prevent accidentally writing the resolution register to a higher resolution and exceeding the maximum temperature conversion time of t conv = 125 ms, a shut- down command (using the config regis- ter) is required to change the resolution register. the device must be in shutdown mode to change the resolution. register 5-8: resolution register ? 0000 1001b r/w-0 u-0 u-0 u-0 u-0 u-0 u-0 u-0 bit 15 bit 8 u-0 u-0 u-0 u-0 u-0 u-0 r/w-0 r/w-1 resolution bit 7 bit 0 legend: r = readable bit w = writable bit u = unimplemented bit, read as 0 -n = value at por 1 = bit is set 0 = bit is cleared x = bit is unknown bit 15 unimplemented: read as 0 bit 14-2 unimplemented: read as 0 bit 1-0 resolution: 00 = lsb = 0.5c (t conv = 30 ms, typical) 01 = lsb = 0.25c (power-up default, t conv = 65 ms, typical) 10 = lsb = 0.125c (t conv = 130 ms, typical) 11 = lsb = 0.0625c (t conv = 260 ms, typical) downloaded from: http:///
? 2013 microchip technology inc. ds20005192b-page 27 mcp9844 5.2 sensor feature description 5.2.1 shutdown mode shutdown mode disables all power-consuming activities (including temperature sampling operations) while leaving the serial interface active. this mode is selected by setting bit 8 of config to 1 . in this mode, the device consumes i shdn . it remains in this mode until bit 8 is cleared 0 to enable continuous conversion mode, or until power is recycled. the shutdown bit (bit 8) cannot be set to 1 while bits 6 and 7 of config (lock bits) are set to 1 . however, it can be cleared 0 or returned to continuous conversion while locked. in shutdown mode, all registers can be read or written. however, the serial bus activity increases the shutdown current. if the device is shutdown while the event pin is asserted, then the event output will be deasserted during shutdown. it will remain deasserted until the device is enabled for normal operation. once the device is enabled, it takes t conv before the device reasserts the event output. 5.2.2 temperature hysteresis (t hyst ) a hysteresis of 0c, 1.5c, 3c or 6c can be selected for the t upper , t lower and t crit temperate boundaries using bits 10 and 9 of config. the hysteresis applies for decreasing temperature only (hot to cold), or as temperature drifts below the specified limit. the hysteresis bits can not be changed if either of the lock bits, bits 6 and 7 of config, are set to 1 . the t upper , t lower and t crit boundary conditions are described graphically in figure 5-9 . 5.2.3 event output configuration the event output can be enabled using bit 3 of config (event output control bit) and can be configured as either a comparator output or as interrupt output mode using bit 0 of config (event mode). the polarity can also be specified as an active-high or active-low using bit 1 of config (event polarity). the event output requires a pull-up resistor to function. these configurations are designed to serve processors with low-to-high or high-to-low edge triggered inputs. with active-high configuration, when the event output deasserts, power will be dissipated across the pull-up resistor. when the ambient temperature increases above the critical temperature limit, the event output is forced to a comparator output (regardless of bit 0 of config). when the temperature drifts below the critical temperature limit minus hysteresis, the event output automatically returns to the state specified by bit 0 of config. the status of the event output can be read using bit 4 of config (event status). this bit can not be set to 1 in shutdown mode. bit 7 and 6 of the config register can be used to lock the t upper , t lower and t crit registers. the bits prevent false triggers at the event output due to an accidental rewrite to these registers. the event output can also be used as a critical temperature output using bit 2 of config (critical output only). when this feature is selected, the event output becomes a comparator output. in this mode, the interrupt output configuration (bit 0 of config) is ignored. downloaded from: http:///
mcp9844 ds20005192b-page 28 ? 2013 microchip technology inc. 5.2.3.1 comparator mode comparator mode is selected using bit 0 of config. in this mode, the event output is asserted as active-high or active-low using bit 1 of config. figure 5-9 shows the conditions that toggle the event output. if the device enters shutdown mode with asserted event output, the output will deassert. it will remain deasserted until the device enters continuous conver- sion mode and after the first temperature conversion is completed, t conv . after the initial temperature conver- sion, t a must satisfy the t upper or t lower boundary conditions in order for event output to be asserted. comparator mode is useful for thermostat type applications, such as turning on a cooling fan or triggering a system shutdown when the temperature exceeds a safe operating range. 5.2.3.2 interrupt mode in interrupt mode, the event output is asserted as active- high or active-low (depending on the polarity configuration) when t a drifts above or below t upper and t lower limits. the output is deasserted by setting bit 5 (interrupt clear) of config. if the device enters shutdown mode with asserted event output, the output will deassert. it will remain deasserted until the device enters continuous conversion mode and after the first temperature conversion is completed, t conv . if the inter- rupt clear bit (bit 5) is never set, then the event output will reassert after the first temperature conversion. in addition, if t a >= t crit , the event output is forced as comparator mode and asserts until t a < t crit - t hyst . while the event output is asserted, the user must send a clear interrupt command (bit 5 of config) for the event output to deassert when the temperature drops below the critical limit, t a < t crit - t hyst . otherwise, the event out- put remains asserted (see figure 5-9 for a graphical description). switching from interrupt mode to compara- tor mode also deasserts event output. this mode is designed for interrupt driven microcontroller- based systems. the microcontroller receiving the interrupt will have to acknowledge the interrupt by setting bit 5 of the config register from the mcp9844. 5.2.4 temperature resolution the mcp9844 device is capable of providing tempera- ture data with 0.5c to 0.0625c resolution. the resolution can be selected using the resolution register ( register 5-8 ), which is located in address 00001001 b. this address location is not specified in jedec standard jc42.4. however, it provides additional flexibility while being functionally compatible with jc42.4 and provides a 0.25c resolution at 125 ms (max.). in order to prevent accidentally chang- ing the resolution and exceeding the 125 ms conver- sion time, the device must be in shutdown mode to change this register. the selected resolution can be read by the user using bit 4 and bit 3 of the capability register ( register 5-2 ). a 0.25c resolution is set as por default by the factory. table 5-2: temperature conversion time resolution t conv (ms) samples/sec (typical) 0.5c 30 33 0.25c (power-up default) 65 15 0.125c 130 8 0.0625c 260 4 downloaded from: http:///
? 2013 microchip technology inc. ds20005192b-page 29 mcp9844 figure 5-9: event output condition. t upper t lower event output t crit t a t upper - t hyst (active-low) comparator interrupt s/w int. clear critical only t crit - t hyst 1 2 3 4 5 7 table 5-9: temperature event output conditions note output boundary conditions comparator interrupt critical t a bits output state (active low/high) 15 14 13 1t a ?? t lower high/low low/high high/low 000 2t a ? t lower - t hyst low/high low/high high/low 001 3t a ?? t upper low/high low/high high/low 010 4 t a ? t upper - t hyst high/low low/high high/low 000 5 t a ? t crit low/high low/high low/high 110 6 when t a ?? t crit, the event output is forced to comparator mode and bits 0 of config (event output mode) is ignored until t a ? t crit - t hyst . in interrupt mode, if interrupt is not cleared (bits 5 of config) as shown in the diagram at note 6 , then the event will remain asserted at note 7 until the interrupt is cleared by the controller. 7t a ? t crit - t hyst low/high high/low high/low 010 t lower - t hyst t lower -t hyst t upper - t hyst 1 3 4 2 note: 6 event output (active-high) comparator interrupt s/w int. clear critical only downloaded from: http:///
mcp9844 ds20005192b-page 30 ? 2013 microchip technology inc. 5.3 summary of power-on default the mcp9844 has an internal power-on reset (por) circuit. if the power supply voltage v dd glitches down to the v por_ts and v por_ee thresholds, the device resets the registers to the power-on default settings. table 5-3 shows the power-on default summary for the temperature sensor. table 5-3: mcp9844 temperature sensor power-on reset defaults registers default register data (hexadecimal) power-up default register description address (hexadecimal) register name 0x00 capability 0x00ef event output deasserts in shutdown i 2 c? time out 25 ms to 35 ms. accepts v hv at a0 pin 0.25c measurement resolution measures temperature below 0c 1c accuracy over active range temperature event output 0x01 config 0x0000 comparator mode active-low output event and critical output output disabled event not asserted interrupt cleared event limits unlocked critical limit unlocked continuous conversion 0c hysteresis 0x02 t upper 0x0000 0c 0x03 t lower 0x0000 0c 0x04 t crit 0x0000 0c 0x05 t a 0x0000 0c 0x06 manufacturer id 0x0054 0x07 reserved 0x0601 0x08 microchip device id/ device revision 0x0601 0x09 resolution 0x0001 most significant bit is set by default 0.25c measurement resolution downloaded from: http:///
? 2013 microchip technology inc. ds20005192b-page 31 mcp9844 6.0 applications information 6.1 layout considerations the mcp9844 device does not require any additional components besides the master controller in order to measure temperature. however, it is recommended that a decoupling capacitor of 0.1 f to 1 f be used between the v dd and gnd pins. a high-frequency ceramic capacitor is recommended. it is necessary for the capacitor to be located as close as possible to the power and ground pins of the device in order to provide effective noise protection. in addition, good pcb layout is key for better thermal conduction from the pcb temperature to the sensor die. for good temperature sensitivity, add a ground layer under the device pins as shown in figure 6-1 . 6.2 thermal considerations a potential for self-heating errors can exist if the mcp9844 sda, sclk and event lines are heavily loaded with pull-ups (high current). typically, the self- heating error is negligible because of the relatively small current consumption of the mcp9844. a temperature accuracy error of approximately 0.5c could result from self-heating if the communication pins sink/source the maximum current specified. for example, if the event output is loaded to maximum i ol , equation 6-1 can be used to determine the effect of self-heating. equation 6-1: effect of self- heating at room temperature (t a = +25c) with maximum i dd = 500 a and v dd = 3.6v, the self-heating due to power dissipation t ? is 0.58c for the tdfn-8 package. figure 6-1: tdfn package layout. t ? ? ja v dd i dd v ol_event i ol_event v ol_sda i ol_sda ? + ? + ? ?? = where: t ? =t j - t a t j = junction temperature t a = ambient temperature ? ja = package thermal resistance v ol_event, sda = event and sda output v ol (0.4 v max ) i ol_event, sda = event and sda output i ol (3 ma max and 20 ma max, respectively) a0a1 a2 gnd v dd event scl sda ep9 downloaded from: http:///
mcp9844 ds20005192b-page 32 ? 2013 microchip technology inc. 7.0 packaging information 7.1 package marking information legend: xx...x customer-specific information y year code (last digit of calendar year) yy year code (last 2 digits of calendar year) ww week code (week of january 1 is week 01) nnn alphanumeric traceability code pb-free jedec ? designator for matte tin (sn) * this package is pb-free. the pb-free jedec designator ( ) can be found on the outer packaging for this package. note : in the event the full microchip part number cannot be marked on one line, it will be carried over to the next line, thus limiting the number of available characters for customer-specific information. 3 e 3 e 8-lead tdfn (2x3) (mcp9844) example: part number code mcp9844t-be/mny abs abs 310 25 downloaded from: http:///
? 2013 microchip technology inc. ds20005192b-page 33 mcp9844 note: for the most current package drawings, please see the microchip packaging specification located at http://www.microchip.com/packaging downloaded from: http:///
mcp9844 ds20005192b-page 34 ? 2013 microchip technology inc. note: for the most current package drawings, please see the microchip packaging specification located at http://www.microchip.com/packaging downloaded from: http:///
? 2013 microchip technology inc. ds20005192b-page 35 mcp9844 downloaded from: http:///
mcp9844 ds20005192b-page 36 ? 2013 microchip technology inc. appendix a: revision history revision b (july 2014) the following is the list of modifications. 1. updated the serial interface timing specifi- cations section to include 400 khz operation from 1.7v to 3.6v. 2. updated the temperature sensor dc charac- teristics table. 3. updated verbiage throughout the document. revision a (march 2013) original release of this document. downloaded from: http:///
? 2013 microchip technology inc. ds20005192b-page 37 mcp9844 product identification system to order or obtain information, e. g., on pricing or delivery, refer to the factory or the listed sales office . device: mcp9844t: temperature sensor temperature range: e = -40c to +125c (extended) package: mny* = plastic dual flat, no lead, (2x3 tdfn), 8-lead (tdfn) * y = nickel palladium gold manufacturing designator. only available on the tdfn package. part no. /xx package temperature range device examples: a) mcp9844t-be/mny: tape and reel, extended temp., 8ld 2x3 tdfn pkg. -x downloaded from: http:///
mcp9844 ds20005192b-page 38 ? 2013 microchip technology inc. notes: downloaded from: http:///
? 2013-2014 microchip technology inc. ds20005192b-page 39 information contained in this publication regarding device applications and the like is provided only for your convenience and may be superseded by updates. it is your responsibility to ensure that your application meets with your specifications. microchip makes no representations or warranties of any kind whether express or implied, written or oral, statutory or otherwise, related to the information, including but not limited to its condition, quality, performance, merchantability or fitness for purpose . microchip disclaims all liability arising from this information and its use. use of microchip devices in life support and/or safety applications is entirely at the buyers risk, and the buyer agrees to defend, indemnify and hold harmless microchip from any and all damages, claims, suits, or expenses resulting from such use. no licenses are conveyed, implicitly or otherwise, under any microchip intellectual property rights. trademarks the microchip name and logo, the microchip logo, dspic, flashflex, flexpwr, jukeblox, k ee l oq , k ee l oq logo, kleer, lancheck, medialb, most, most logo, mplab, optolyzer, pic, picstart, pic 32 logo, righttouch, spynic, sst, sst logo, superflash and uni/o are registered trademarks of microchip tec hnology incorporated in the u.s.a. and other countries. the embedded control solutions company and mtouch are registered trademarks of microchip technology incorporated in the u.s.a. analog-for-the-digital age, bodycom, chipkit, chipkit logo, codeguard, dspicdem, dspicdem.net, ecan, in-circuit serial programming, icsp, inter-chip connectivity, kleernet, kleernet logo, miwi, mpasm, mpf, mplab certified logo, mplib, mplink, multitrak, netdetach, omniscient code generation, picdem, picdem.net, pickit, pictail, righttouch logo, real ice, sqi, serial quad i/o, total endurance, tsharc, usbcheck, varisense, viewspan, wiperlock, wireless dna, and zena are trademarks of microchip technology incorporated in the u.s.a. and other countries. sqtp is a service mark of microchip technology incorporated in the u.s.a. silicon storage technology is a registered trademark of microchip technology inc. in other countries. gestic is a registered trademar ks of microchip technology germany ii gmbh & co. kg, a subsidiary of microchip technology inc., in other countries. all other trademarks mentioned herein are property of their respective companies. ? 2013-2014, microchip technology incorporated, printed in the u.s.a., all rights reserved. isbn: 978-1-63276-397-6 note the following details of the code protection feature on microchip devices: microchip products meet the specification cont ained in their particular microchip data sheet. microchip believes that its family of products is one of the most secure families of its kind on the market today, when used i n the intended manner and under normal conditions. there are dishonest and possibly illegal methods used to breach the code protection feature. all of these methods, to our knowledge, require using the microchip products in a manner outside the operating specif ications contained in microchips data sheets. most likely, the person doing so is engaged in theft of intellectual property. microchip is willing to work with the customer who is concerned about the integrity of their code. neither microchip nor any other semiconduc tor manufacturer can guarantee the security of their code. code protection does not mean that we are guaranteeing the product as unbreakable. code protection is constantly evolving. we at microchip are co mmitted to continuously improvin g the code protection features of our products. attempts to break microchips code protection feature may be a violation of the digital millennium copyright act. if such acts allow unauthorized access to your software or other copyrighted work, you may have a right to sue for relief under that act. microchip received iso/ts-16949:2009 certification for its worldwide headquarters, design and wafer fabrication facilities in chandler and tempe, arizona; gresham, oregon and design centers in california and india. the company?s quality system processes and procedures are for its pic ? mcus and dspic ? dscs, k ee l oq ? code hopping devices, serial eeproms, microperipherals, nonvolatile memory an d analog products. in addition, microchip?s quality system for the design and manufacture of development systems is iso 9001:2000 certified. quality management s ystem certified by dnv == iso/ts 16949 == downloaded from: http:///
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