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mic280 precision ittybitty? thermal supervisor ittybitty is a trademark of micrel, inc. all other tra demarks are the property of their respective owners. micrel inc. ? 2180 fortune drive ? san jose, ca 95131 ? usa ? tel +1 (408) 944- 0800 ? fax + 1 (408) 474 - 1000 ? http://www.micrel.com may 5 , 20 14 revision 2.0 general description the mic280 is a digital thermal supervisor capable of measuring its own internal temperature and that of a remote pn junction. the remote junction may be an inexpensive commodity transistor e.g., 2n3906 or an embedded thermal diode such as those found in intel pentium ? ii/iii/iv cpus, amd athlon ? cpus, and xilinx virtex ? fpgas. a 2-wire smbus ? 2.0 -compatible serial interface is provided for host communication. remote temperature is measured with 1c accuracy and 9-bit to 12 -bit resolution (programmable). independent high, low, and overtemperature thresholds are provided for each zone. the advanced integrating a/d converter and analog front- end reduce errors due to noise for maximum accuracy and minimum guardbanding. the interrupt output signals temperature events to the host, including data-ready and diode faults. critical device settings can be locked to prevent changes and ensure failsafe operation. the clock, data, and interrupt pins are 5v-tolerant regardless of the value of v dd . they will not clamp the bus lines low even if the device is powered down. superior accuracy, failsafe operation, and small size make the mic280 an excellent choice for the most demanding thermal management applications. datasheets and support documentation are available on micrels web site at : www.micrel.com . features ? measures local and remote temperature ? highly accurate remote sensing: 1c max., 60c to 100c ? superior noise immunity for reduced temperature guardbands ? 9-bit to 12-bit temperature resolution for remote zone ? fault queues to further reduce nuisance tripping ? programmable high, low, and overtemperature thresholds for each zone ? smbus 2.0-compatible serial interface including device timeout to prevent bus lockup ? voltage-tolerant i/os ? open-drain interrupt output pin C supports smbus alert response address protocol ? low power shutdown mode ? locking of critical functions to ensure failsafe operation ? failsafe response to diode faults ? enables acpi-compliant thermal management ? 3.0v to 3.6v power supply range ? available in ittybitty ? sot23-6 package applications ? desktop, server, and notebook computers ? printers and copiers ? test and measurement equipment ? thermal supervision of xilinx virtex fpgas ? wireless/rf systems ? intelligent power supplies ? datacom/telecom cards typical application downloaded from: http:///
micrel, inc. mic280 may 5 , 20 14 2 revision 2.0 ordering information part number marking slave address ambient temp. range package mic280-0ym6 ta 00 100 1000 b C 55 to +125c sot23-6 mic280-1ym6 ta 01 100 1001 b C 55 to +125c sot 23 -6 mic2 80 -2ym6 ta 02 100 1010 b C 55 to +125c sot23-6 mic280-3ym6 ta 03 100 1011 b C 55 to +125c sot23-6 mic280-4ym6 ta 04 100 1100 b C 55 to +125c sot23-6 mic280-5ym6 ta 05 100 1101 b C 55 to +125c sot23-6 mic280-6ym6 ta 06 100 1110 b C 55 to +125c sot23-6 mic280-7ym6 ta 07 100 1111 b C 55 to +125c sot23-6 note: 1. underbar (_) may not be to scale. pin configuration sot23-6 (m6) (top view) pin description pin number pin name pin function 1 vdd power supply input. 2 gnd ground. 3 t1 analog input. connection to remote diode junction. 4 clk digital input. serial bit clock input. 5 data digital input/output. open-drain. serial data input/output. 6 /int digital output. open-drain. interrupt output. downloaded from: http:///
micrel, inc. mic280 may 5 , 20 14 3 revision 2.0 absolute maximum ratings ( 2 ) power supply voltage (v dd ) ........................................ +3.8v voltage on t1 ....................................... C 0.3v to v dd + 0.3v voltage on clk, data, /int ............................. C 0.3v to 6v current into any pin .................................................. 10ma power dissipation, t a = +125c .............................. 109mw storage temperature (ts) ......................... C 65 c to +150 c esd ratings ( 4 ) human body model ..................................................... 1.5 kv machine model ............................................................. 200v soldering (sot23-6 package) vapor phase (60s) ........................................... 220 c +5 / -0 c infrared (15s) .................................................... 235 c +5 / -0 c operating ratings ( 3 ) power supply voltage (v dd ) ........................ +3.0v to +3.6v ambient temperature range (t a ) ............ C 55c to +125c junction temperature .............................................. +150c junction thermal resistance sot23-6 ( ? ja ) .................................................. 230c/w electrical characteristics ( 5 , 6 ) v dd = 3.3v ; t a = 25c, unless noted. b old values indicate C 55 c t a +125c, 3.0v v dd 3.6v, unless noted ( 3 ) . symbol parameter condition min. typ. max. units power supply i dd supply current /int, t1 open; clk = data = high; normal mode 0.23 0.4 ma shutdown mode; /int, t1 open; note 7 clk = 100khz, data = high 9 a shutdown mode; /int, t1 open; clk = data = high 6 a t por power-on reset time, note 7 v dd > v por 200 s v por power-on reset voltage all registers reset to default values; a/d conversions initiated 2.65 2.95 v v hyst power- on reset hysteresis voltage, note 7 300 mv temperature- to -digital converter characteristics accuracy, remote temperature notes 3 , 9 , 12 , 13 60 c t d 100 c 3.15v < v dd < 3.45v, 25c < t a < 85c 0.25 1 c 0 c t d 100 c 3.15v < v dd < 3.45v, 25c < t a < 85c 1 2 c C 55 c t d 125 c 3.15v < v dd < 3.45v, 25c < t a < 85c 2 4 c accuracy, local temperature notes 3 , 12 0 c t a 100 c, 3.15v < v dd < 3.45v 1 2 c C 55 c t a 125 c, 3.15v < v dd < 3.45v 1.5 2.5 c t conv conversion time notes 3 , 10 res[1:0]=00 (9 bits) 200 240 ms res[1:0]=01 (10 bits) 330 390 ms res[1:0]=10 (11 bits) 570 670 ms res[1:0]=11 (12 bits) 1000 1250 ms downloaded from: http:///
micrel, inc. mic280 may 5 , 20 14 4 revision 2.0 electrical characteristics ( 5 , 6 ) (continued) v dd = 3.3v; t a = 25c, unless noted. b old values indicate C 55 c t a +125c, 3.0v v dd 3.6v, unless noted ( 3 ) . symbol parameter condition min. typ. max. units remote temperature input, t1 i f cu rrent into external diode note 7 t1 forced to 1.0v, high level 192 400 a low level 7 12 a serial data i/o pin, data v ol low output voltage, note 6 i ol = 3ma 0.3 v i ol = 6ma 0.5 v v il low input voltage 3v v dd 3.6v 0.8 v v ih high input voltage 3v v dd 3.6v 2.1 5.5 v c in input capacitance note 7 10 pf i leak input current 1 a serial clock input, clk v il low input voltage 3v v dd 3.6v 0.8 v v ih high input voltage 3v v dd 3.6v 2.1 5.5 v c in input capacitance note 7 10 pf i leak input current 1 a interrupt output, /int v ol low output voltage, note 6 i ol = 3ma 0.3 v i ol = 6ma 0.5 v t int interrupt propagation delay notes 7 , 8 from tempx < tlowx or tempx > thighx or tempx > critx to /int < v ol , r pullup = 10k ? [t conv ] ms t nint interrupt reset propagation delay, notes 7 , 11 from read of status or a.r.a. to /int > v oh r pullup = 10k ? 1 s i leak 1 a downloaded from: http:///
micrel, inc. mic280 may 5 , 20 14 5 revision 2.0 electrical characteri stics ( 5 , 6 ) (continued) v dd = 3.3v; t a = 25c, unless noted. b old values indicate C 55 c t a +125c, 3.0v v dd 3.6v, unless noted ( 3 ) . symbol parameter condition min. typ. max. units serial interface timing t 1 clk (clock) period 2.5 s t 2 data in setup time to clk high 100 ns t 3 data out stable after clk low 300 ns t 4 data low setup time to clk low start condition 100 ns t 5 data high hold time after clk high stop condition 100 ns t to bus timeout 25 30 35 ms notes: 2. exceeding the absolute maximum ratings may damage the device. 3. the device is not guaranteed to function outside its opera ting ratings. final test on outgoing product is performed at t a = 25 c. 4. devices are esd sensitive. handling precautions are re commended. human body model, 1.5k ? in series with 100pf. 5. specification for packaged product only. 6. current into the /int or data pins will result in self hea ting of the device. sink current should be minimized for bes t accuracy. 7. guaranteed by design over the operating temperature ran ge. not 100% production tested. 8. t int and t crit are equal to t conv . 9. t d is the temperature of the remote diode junction. testing is per formed using a single unit of one of the transistors liste d in table 8. 10. t conv = t conv (local) + t conv (remote). following the acquisition of either remote or local te mperature data, the limit comparisons for that zone are performed and the device status updated. status bits will be set and /int driven active, if applicable. 11. the interrupt reset propagation delay is dominated by the capacitance on the bus. 12. accuracy specification does not include quantization noise, which may be up to 1/2 lsb. 13. tested at 10-bit resolution. downloaded from: http:///
micrel, inc. mic280 may 5 , 20 14 6 revision 2.0 timing diagram serial interface timing downloaded from: http:///
micrel, inc. mic280 may 5 , 20 14 7 revision 2.0 typical characteristics downloaded from: http:///
micrel, inc. mic280 may 5 , 20 14 8 revision 2.0 typical characteristics (continued) downloaded from: http:///
micrel, inc. mic280 may 5 , 20 14 9 revision 2.0 functional description serial port operation the mic280 uses standard smbus write_byte, read_byte, and read_word operations for communication with its host. the smbus write_byte operation involves sending the devices slave address (with the r/w bit low, to signal a write operation), followed by a command byte and the data byte. the smbus read_byte operation is a composite write and read operation: the host ?rst sends the devices slave address followed by the command byte, as in a write operation. a new start bit must then be sent to the mic280, followed by a repeat of the slave address with the r/w bit (lsb) set to the high (read) state. the data to be read from the part may then be clocked out. a read_word is similar, but two successive data bytes are clocked out rather than one. these protocols are shown in figure 1, figure 2, and figure 3. the command byte is eight bits (one byte) wide. this byte carries the address of the mic280 register to be operated upon. the command byte values corresponding to the various mic280 registers are shown in table 2 . other command byte values are reserved, and should not be used. slave address the mic280 will only respond to its own unique slave address. a match between the mic280s address and the address speci?ed in the serial bit stream must be made to initiate communication. the mic280s slave address is ?xed at the time of manufacture. eight different slave addresses are available as determined by the part number. see table 1 below and the ordering information table. table 1. mic280 slave addresses part number slave address mic280-0y m6 100 1000 b = 48 h mic280- 1y m6 100 1001 b = 49 h mic280- 2y m6 100 1010 b = 4a h mic280- 3y m6 100 1011 b = 4b h mic280- 4y m6 100 1100 b = 4c h mic280- 5y m6 100 1101 b = 4d h mic280- 6y m6 100 1110 b = 4e h mic280- 7y m6 100 1111 b = 4f h table 2. mic280 register addresses target register command byte value power- on default label description read write temp0 local temperature result 00 h n/a 00 h (0 c) temp1h remote temperature result, high byte 01 h n/a 00 h (0 c) status status 02 h n/a 00 h config configuration 03 h 03 h 80 h imask interrupt mask register 04 h 04 h 07 h thigh0 local temperature high limit 05 h 05 h 3c h (60 c) tlow0 local temperature low limit 06 h 06 h 00 h (0 c) thigh1h remote temperature high limit, high byte 07 h 07 h 50 h (80 c) tlow1h remote temperature low limit, high byte 08 h 08 h 00 h (0 c) lock security register 09 h 09 h 00 h temp1l remote temperature result, low byte 10 h n/a 00 h thigh1l remote temperature high limit, low byte 13 h 13 h 00 h tlow1l remote temperature low limit, low byte 14 h 14 h 00 h crit1 remote overtemperature limit 19 h 19 h 64 h (100 c) crit0 local overtemperature limit 20 h 20 h 46 h (70 c) mfg_id manufacturer identification fe h n/a 2a h dev_id device and revision identification ff h n/a 0x h * *the lower nibble contains the die revision level, e.g., rev 0 = 00h. downloaded from: http:///
micrel, inc. mic280 may 5 , 20 14 10 revision 2.0 alert response address in addition to the read_byte, write_byte, and read_word protocols, the mic280 adheres to the smbus protocol for response to the alert response address (ara). the mic280 expects to be interrogated using the ara when it has as- serted its /int output. temperature data format the lea st - signi?cant bit of each temperature register (high bytes) represents one degree centigrade. the values are in a twos complement format, wherein the most signi?cant bit (d7) represents the sign: zero for positive temperatures and one for negative temperatures. table 3 shows examples of the data used by the mic280 for temperatures. table 3. digital temperature format, high bytes temperature binary hex +127c 0111 1111 7f +125c 0111 1101 7d +25c 0001 1001 19 +1 c 0000 0001 01 0c 0000 0000 00 C 1c 1111 1111 ff C 25 c 1110 0111 e7 C 125 c 1000 0011 83 C 128 c 1000 0000 80 extended temperature resolution is provided for the external zone. the high and low temperature limits and the measured temperature for zone one are reported as 12 -bit values stored in a pair of 8-bit registers. the measured temperature, for example, is reported in registers temp1h, the high-order byte, and temp1l, the low-order byte. the values in the low-order bytes are left- justi?ed four -bit binary values representing one-sixteenth degree increments. the a-d converter resolution for zone 1 is selectable from nine to twelve bits via the con?guration register. low-order bits beyond the resolution selected will be reported as zeroes. examples of this format are shown in table 5. fault queue a set of fault queues (progra mmable digital ?lters) are provided in the mic280 to prevent false tripping due to thermal or electrical noise. two bits, config[5:4], set the depth of the fault queues. the fault queue setting then determines the number of consecutive temperature events (tempx > thighx or tempx < tlowx) which must occur in order for the condition to be considered valid. as an example, assume config[5:4] is programmed with 10b. the measured temperature for a given zone would have to exceed thighx for four consecutive a/d conversions before /int would be asserted or the status bit set. like any ?lter, the fault queue function also has the effect of delaying the detection of temperature events. in this example, it would take 4 t conv to detect a temperature event. the fault queue depth versus config[5:4] of the con?guration register is shown in table 4. note: there is no fault queue for overtemperature events (crit0 and crit1) or diode faults. the fault queue applies only to high-temperature and low-temperature events as determined by the thighx and tlowx registers. any write to config will result in the fault queues being purged and reset. writes to any of the limit registers, tlowx or thighx, will result in the fault queue for the corresponding zone being purged and reset. table 4. fault queue depth settings config[5:4] fault queue depth 00 1 (default) 01 2 10 4 11 6 downloaded from: http:///
micrel, inc. mic280 may 5 , 20 14 11 revision 2.0 table 5. digital temperature format, low bytes extended temperature low byte resolution 9 bits 10 bits 11 bits 12 bits binary hex binary hex binary hex binary hex 0.0000 0000 0000 00 0000 0000 00 0000 0000 00 0000 0000 00 0.0625 0000 0000 00 0000 0000 00 0000 0000 00 0001 0000 10 0.1250 0000 0000 00 0000 0000 00 0010 0000 20 0010 0000 20 0.2500 0000 0000 00 0100 0000 40 0100 0000 40 0100 0000 40 0.5625 1000 0000 80 1000 0000 80 1000 0000 80 1001 0000 90 0.9375 1000 0000 80 1100 0000 c0 1110 0000 e0 1111 0000 f0 interrupt generation there are eight different conditions that will cause the mic280 to set one of the bits in status and assert its /int output, if so enabled. these conditions are listed in table 6. unlike previous generations of thermal supervisor ics, there are no interdependencies between any of these conditions. that is, if condition is true, the mic280 will respond accordingly, regardless of any previous or currently pending events. normally when a temperature event occurs, the corresponding status bit will be set in status, the corresponding interrupt mask bit will be cleared, and /int will be asserted. clearing the interrupt mask bit(s) prohibits continuous interrupt generation while the device is being serviced. it is possible to prevent events from clearing interrupt mask bits by setting bits in the lock register. se e table 7 for lockbit functionality. a temperature event will only set bits in the status register if it is speci?cally enabled by the corresponding bit i n the interrupt mask register. an interrupt signal will only be generated on /int if interrupts are also globally enabled (ie = 1 in config). the mic280 expects to be interrogated using the alert re sponse address once it has asserted its interrupt output. following an interrupt, a successful response to the a.r.a. or a read operation on status will cause /int to be de-asserted. status will also be cleared by the read operation. reading status following an interrupt is an acceptable substitute for using the a.r.a. if the host system does not implement the a.r.a protocol. figure 4 and figure 5 illustrate these two methods of responding to mic280 interrupts. because temperature- to -digital conversions continue while /int is asserted, the measured temperature could change between the mic280s assertion of /int and the hosts response. it is good practice for the interrupt service routine to read the value in tempx to verify that the overtemperature or undertemperature condition still exists. in addition, more than one temperature event may have occurred simultaneously or in rapid succession between the assertion of /int and servicing of the mic280 by the host. the interrupt service routine should allow for this eventuality. at the end of the interrupt service routine, the interrupt enable bits should be reset to permit future interrupts. reading the result registers all mic280 registers are eight bits wide and may be accessed using the standard read_byte protocol. the temperature result for the local zone, zone 0, is a single 8-bit value in register temp0. a single read_byte operation by the host is suf?cient for retrieving this value. the temperature result for the remote zone is a twelve-bit value split across two eight- bi t registers, temp1h and temp1l. a series of two read_byte operations are needed to obtain the entire twelve-bit temperature result for zone 1. it is possible under certain conditions that the temperature result for zone 1 could be updated between the time temp1l or temp1h is read and the companion register is read. in order to ensure coherency, temp1h supports the use of the read_word protocol for accessing both temp1h and temp1l with a single operation. this ensures that the values in both result registers are from the same adc cycle. this is illustrated in figure 3. read_word operations are only supported for temp1h: temp1l, i.e., only for command byte values of 01h. polling the mic280 may either be polled by the host or request the hosts attention via th e /int pin. in the case of polled operation, the host periodically reads the contents of status to check the state of the status bits. the act of reading status clears it. if more than one event that sets a given status bit occurs before the host polls status, only the fact that at least one such event has occurred will be apparent to the host. for polled systems, the global interrupt enable bit should be clear (ie = 0). this will disable interrupts from the mic280 (prevents the /int pin from sinking current). for interrupt-driven systems, ie must be set to enable the /int output. downloaded from: http:///
micrel, inc. mic280 may 5 , 20 14 12 revision 2.0 shutdown mode putting the device into shutdown mode by setting the shutdown bit in the con?guration register will unconditionally deassert /int, clear status, and purge the fault queues. therefore, this should not be done before completing the appropriate interrupt service routine(s). no other registers will be affected by enterin g shutdown mode. the last temperature readings will persist in the tempx registers. the mic280 can be prevented from entering shutdown mode using the shutdown lockout bit in the lock register. if l3 in lock is set while the mic280 is in shutdown mode, it will immediately exit shutdown mode and resume normal operation. it will not be possible to subsequently re-enter shutdown mode. if the reset bit is set while the mic280 is shut down, normal operation resumes from the reset state. warm resets the mic280 can be reset to its power-on default state during operation by setting the rst bit in the con?guration register. when this bit is set, /int will be deasserted, the fault queues will be purged, the limit registers will be restored to their normal power-on default values, and any a/d conversion in progress will be halted and the results discarded. this includes reset- ting bits l3 - l0 in the security register, lock. the state of the mic280 following this operation is indistinguishable from a power-on reset. if the reset bit is set while the mic280 is shut down, the shutdown bit is cleared and normal operation resumes from the reset state. if bit 4 of lock, the warm reset lockout bit, is set, warm resets cannot be initiated, and writes to the rst bit will be completely ignored. setting l4 while the mic280 is shut down will result in the device exiting shutdown mode and resuming normal operation, just as if the shutdown bit had been cleared. table 6. mic280 temperature events event condition mic280 response ( 14 ) data ready a/d conversions complete for both zones; result registers updated; state of /int updated set s7, clear im7, assert /int overtemperature, remote ([temp1h:temp1l]) >crit1 set s1, assert /int overtemperature, local temp0 >crit0 set s0, assert /int high temperature, remote ([temp1h:temp1l]) >[thigh1h:thigh1l] ( 15 ) set s4, clear im4, assert /int high temperature, local temp0 >thigh0 ( 15 ) set s6, clear im6, assert /int low temperature, remote ([temp1h:temp1l]) <[tlow1h:tlow1l] ( 15 ) set s3, clear im3, assert /int low temperature, local temp0 micrel, inc. mic280 may 5 , 20 14 13 revision 2.0 figure 1. write_byte protocol figure 2. read_byte protocol figure 3. read_word protocol for accessing temp1h : temp1l downloaded from: http:///
micrel, inc. mic280 may 5 , 20 14 14 revision 2.0 figure 4. mic280 alert response address protocol figure 5. reading status in response to an interrupt downloaded from: http:///
micrel, inc. mic280 may 5 , 20 14 15 revision 2.0 configuration locking the security register, lock, provides the ability to disable con?guration changes as they apply to the mic280s most critical functions: shutdown mode, and reporting diode faults and overtemperature events. lock provides a way to prevent malicious or accidental changes to the mic280 registers that might prevent a system from responding properly to critical events. once l0, l1, or l2 has been set, the global interrupt enable bit, ie, will be set and ?xed. it cannot subsequently be cleared. its state will be re?ected in the con?guration register. the bits in lock can only be set once. that is, once a bit is set, it cannot be reset until the mic280 is power-cycled or a warm reset is performed by setting rst in the con?guration register. the warm reset function can be disabled by setting l4 in lock. if l4 is set, locked settings cannot be changed during operation and warm resets cannot be performed; only a power- cycle will reset the locked state(s). if l0 is set, the values of im0 and crit0 become ?xed and unchangeable. that is, writes to crit0 and the corresponding interrupt enable bit are locked out. a local overtemperature event will generate an interrupt regardless of the setting of ie or its interrupt mask bit. if l1 is set, the values of im1 and crit1 become ?xed and unchangeable. a remote over-temperature event will generate an interrupt regardless of the setting of ie or its interrupt mask bit. similarly, setting l2 will ?x the state of im2, allowing the system to permanently enable or disable diode fault interrupts. a diode fault will generate an interrupt regardless of the setting of ie or its interrupt mask bit. l3 can be used to lock out shutdown mode. if l3 is set, the mic280 will not shut down under any circumstances. attempts to set the shdn bit will be ignored and all chip functions will remain operational. if l3 is set while the mic280 is in shutdown mode, it will immediately exit shutdown mode and resume normal operation. it will not be possible to subsequently re-enter shutdown mode. setting l4 disables the rst bit in the con?guration register, preventing the host from initiating a warm reset. writes to rst will be completely ignored if l4 is set. table 7. lock bit functionality lock bit function locked response when s et l0 local over-temperature detection im0 ?xed at 1, writes to crit0 locked -out; ie permanently set l1 remote over-temperature detection im1 ?xed at 1; writes to crit1 locked -out; ie permanently set l2 diode fault interrupts locked on or off im2 ?xed at current state; ie permanently set if im2=1 l3 shutdown mode shdn ?xed at 0; exit shutdown if shdn=1 when l3 is set l4 warm resets rst bit disabled; cannot initiate warm resets downloaded from: http:///
micrel, inc. mic280 may 5 , 20 14 16 revision 2.0 detailed register descriptions local temperature result register (temp0) 8-bits, read-only temperature data from adc local temperature result register d[7] read-only d[6] read-only d[5] read-only d[4] read-only d[3] read-only d[2] read-only d[1] read-only d[0] read-only bit function operation d[7:0] measured temperature data for the local zone. read-only power-up default value: 0000 0000 b = 00 h = (0 c) ( 16 ) read command byte: 0000 0000 b = 00 h each lsb represents one degree centigrade. the values are in a twos complement bi nary format such that 0c is reported as 0000 0000b. see the temperature data format section for more details. note: 16. temp0 will contain measured temperature data after the completion of one conversion. remote temperature result high-byte register (temp1h) 8-bits, read-only temperature data from adc remote temperature result high-byte register d[7] read-only d[6] read-only d[5] read-only d[4] read-only d[3] read-only d[2] read-only d[1] read-only d[0] read-only bit function operation d[7:0] measured temperature data for the remote zone, most significant b yte. read-only power-up default value: 0000 0000 b = 00 h = (0 c) ( 17 ) read command byte: 0000 0001 b = 01 h each lsb represents one degree centigrade. the values are in a twos complement bi nary format such that 0c is reported as 0000 0000b. see the temperature data format section for more details. temp1h can be read using either a read_byte operation or a read_word operation. using rea d_byte will yield the 8-bit value in temp1h. the complete remote temperature result in both temp1h and temp 1l may be obtained by performing a read_word operation on temp1h. the mic280 will respond to a read_word with a command byt e of 01h (temp1h) by returning the value in temp1h followed by the value in temp1l. this guarantees that the data in both registers is from the same temperature- to -digital conversion cycle. the read_word operation is diagrammed in figure 3 . this is the only mic280 register that supports read_word. note: 17. temp0 will contain measured temperature data after the completion of one conversion. downloaded from: http:///
micrel, inc. mic280 may 5 , 20 14 17 revision 2.0 status register (status) 8-bits, read-only status register d[7] read-only d[6] read-only d[5] read-only d[4] read-only d[3] re ad -only d[2] read-only d[1] read-only d[0] read-only s7 s6 s5 s4 s3 s2 s1 s0 bit function operation ( 18 ) s7 data ready 1 = data available, 0 = adc busy s6 local high temperature event 1 = event occurred, 0 = none s5 local low temperature event 1 = event occurred, 0 = none s4 remote high temperature event 1 = event occurred, 0 = none s3 remote low temperature event 1 = event occurred, 0 = none s2 diode fault 1 = fault, 0 = none s1 remote overtemperature event 1 = event occurred, 0 = none s0 local overtemperature event 1 = event occurred, 0 = none note: 18. all status bits are cleared after any read operation is performed on status. power-up default value: 0000 0000 b = 00 h = (no events pending) read command byte: 0000 0010 b = 02 h the power- up default value is 00h. following the ?rst conversion, however, any of the status bits may be set depending on the measured temperature results or the existence of a diode fault. downloaded from: http:///
micrel, inc. mic280 may 5 , 20 14 18 revision 2.0 configuration register (config) 8-bits, read/write configuration register d[7] read/write d[6] read/write d[5] reserved d[4] reserved d[3] reserved d[2] reserved d[1] reserved d[0] reserved interrupt enable (ie) shut-down (shdn) fault queue (fq[1:0]) resolution (res[1:0]) reserved reset (rst) bit function operation ie interrupt enable 1 = interrupts enabled, 0 = disabled shdn selects operating mode: normal/shutdown 1 = shutdown, 0 = normal fq[1:0] depth of fault queue ( 19 ) [00] = 1, [01] = 2, [10] = 4, [11] = 6 res[1:0] a/d converter resolution for external zone; affects conversion rate [00] = 9-bits, [01] = 10-bits, [10] = 11-bits, [11] = 12-bits d[1] reserved always write as zero rst resets all mic280 functions and restores the power-up default state write only; 1 = reset, 0 = normal operation; disabled by setting l4 note: 19. any write to config will result in the fault queues being pu rged and reset and any a/d conversion in progress being a borted and the result discarded. the a/d will begin a new conversion sequence once the write operation is complete. power-up default value: 1000 0000 b = 80 h (not in shutdown mode; interrupts enabled; fault queue depth = 1; resolution = 9-bits) read/write command byte: 0000 0011 b = 03 h downloaded from: http:///
micrel, inc. mic280 may 5 , 20 14 19 revision 2.0 interrupt mask register (imask) 8-bits, read/write interrupt mask register d[7] read/write d[6] read/write d[5] reserved d[4] reserved d[3] reserved d[2] reserved d[1] reserved d[0] reserved im7 im6 im5 im4 im3 im2 im1 im0 bit function operation im7 data-ready event mask 1 = enabled, 0 = disabled im6 local high temperature event mask 1 = enabled, 0 = disabled im5 local low temperature event mask 1 = enabled, 0 = disabled im4 remote high temperature event mask 1 = enabled, 0 = disabled im3 remote low temperature event mask 1 = enabled, 0 = disabled im2 diode fault mask 1 = enabled, 0 = disabled im1 remote overtemperature event mask 1 = enabled, 0 = disabled im0 local overtemperature event mask 1 = enabled, 0 = disabled power-up default value: 0000 01 11 b = 07 h (overtemperature and diode faults enabled) read/write command byte: 0000 0100 b = 04 h local temperature high limit register (thigh0) 8-bits, read/write local temperature high limit register d[7] read/write d[6] read/write d[5] read/write d[4] read/write d[3] read/write d[2] read/write d[1] read/write d[0] read/write high temperature limit for local zone. bit function operation d[7:0] high temperature limit for the local zone. read/write power-up default value: 0011 1100 b = 3c h (60 c) read/write command byte: 0000 0101 b = 05 h each lsb represents one degree centigrade. the values are in a twos complement binary format such that 0c is reported as 0000 0000b. see temperature data format for more details. any writes to a temperature limit register will result in the corresponding fault queu e being purged and reset. downloaded from: http:///
micrel, inc. mic280 may 5 , 20 14 20 revision 2.0 local temperature low limit register (tlow0) 8-bits, read/write local temperature low limit register d[7] read/write d[6] read/write d[5] read/write d[4] read/write d[3] read/write d[2] read/write d[1] read/write d[0] read/write low temperature limit for local zone. bit function operation d[7:0] low temperature limit for the local zone. read/write power-up default value: 0000 0000 b = 00 h (0 c) read/write command byte: 0000 0110 b = 06 h each lsb represents one degree centigrade. the values are in a twos complement binar y format such that 0c is reported as 0000 0000b. see temperature data format for more details. any writes to a temperature limit register will result in the corresponding fault queu e being purged and reset. remote temperature high limit high-byte register (thigh1h) 8-bits, read/write remote temperature high limit high-byte register d[7] read/write d[6] read/write d[5] read/write d[4] read/write d[3] read/write d[2] read/wri te d[1] read/write d[0] read/write high temperature limit for remote zone, most signi?cant byte. bit function operation d[7:0] high temperature limit for the remote zone, most signi?cant byte. read/write power-up default value: 0101 0000 b = 50 h (80 c) read/write command byte: 0000 0111 b = 07 h each lsb represents one degree centigrade. the values are in a twos complement binary format such that 0c is reported as 0000 0000b. see temperature data format for more details. any writes to a temperature limit register will result in the corresponding fault qu eue being purged and reset. downloaded from: http:///
micrel, inc. mic280 may 5 , 20 14 21 revision 2.0 remote temperature low limit high-byte register (tlow1h) 8-bits, read/write remote temperature low limit high-byte register d[7] read/write d[6] read/write d[5] read/write d[4] read/write d[3] read/write d[2] read/write d[1] read/write d[0] read/write low temperature limit for remote zone, most signi?cant byte. bit function operation d[7:0] low temperature limit for the remote zone, most signi?cant byte. read/write power-up default value: 0000 0000 b = 00 h (0 c) read/write command byte: 0000 1000 b = 08 h each lsb represents one degree centigrade. the values are in a twos complement binary format such that 0c is reported as 0000 0000b. see temperature data format for more details. any writes to a temperature limit register will result in the corresponding fault queu e being purged and reset. security register (lock) 8-bits, write once security register d[7] reserved d[6] reserved d[5] reserved d[4] read/write- once d[3] read/write- once d[2] read/write- once d[1] read/write- once d[0] read/write- once reserved l4 l3 l2 l1 l0 bit function operation d[7:5] reserved always write as zero l4 warm-reset lockout bit 1 = rst bit disabled; 0 = unlocked l3 shutdown mode lockout bit ( error! reference source not found. ) 1 = shutdown disabled; 0 = unlocked l2 diode fault event lock bit 1 = locked; 0 = unlocked l1 remote overtemperature event lock bit 1 = locked; 0 = unlocked l0 local overtemperature event lock bit 1 = locked; 0 = unlocked power-up default value: 0000 0000 b = 00 h (all event unlocked) write command byte: 0000 1001 b = 09 h downloaded from: http:///
micrel, inc. mic280 may 5 , 20 14 22 revision 2.0 remote temperature result low -byte register (tlow1l) 8-bits, read only remote temperature result low-byte register d[7] read-only d[6] read-only d[5] read-only d[4] re ad -only d[3] re served d[2] reserved d[1] reserved d[0] reserved temperature data from adc, least significat bits. reserved always reads zero. bit function operation d[7:4] measured temperature data for the remote zone, least significan t bits. read only d[3:0] reserved always reads as zero power-up default value: 0000 0000 b = 00 h (0 c) ( 20 ) read command byte: 0001 0000 b = 10 h each lsb represents one-sixteenth degree centigrade. the values are in a binary f ormat such that 1/16thc (0.0625c) is reported as 0001 0000b. see temperature data format for more details. temp1l can be accessed using a read_byte operation. however, the complete remote temperature result in both temp1h and temp1l may be obtained by performing a read_word operation on temp1h. t he mic280 will respond to a read_word with a command byte of 01h (temp1h) by returning the value in te mp1h followed by the value in temp1l. this guarantees that the data in both registers is from the same temperatu re - to -digital conversion cycle. the read_word operation is diagramed in figure 3. temp1h is the only mic280 register that supports read_word. note: 20. temp1l will contain measured temperature data after the completion of one conversion. remote temperature high limit low-byte register (thigh1l) 8-bits, read/write remote temperature high limit low-byte register d[7] read/write d[6] read/write d[5] read/write d[4] read/write d[3] reserved d[2] reserved d[1] reserved d[0] reserved high temperature limit for remote zone, least significat bits. reserv ed always reads zero. bit function operation d[7:4] high temperature limit for the remote zone, least significant bits . read/write d[3:0] reserved always reads as zero power-up default value: 0000 0000 b = 00 h (0 c) read/write command byte: 0001 00 11 b = 13 h each lsb represents one-sixteenth degree centigrade. the values are in a binary f ormat such that 1/16thc (0.0625c) is reported as 0001 0000b. see temperature data format for more details. any writes to a temperature limit register will result in the corresponding fault queu e being purged and reset. downloaded from: http:///
micrel, inc. mic280 may 5 , 20 14 23 revision 2.0 remote temperature low limit low-byte register (tlow1l) 8-bits, read/write remote temperature low limit low-byte register d[7] read/write d[6] read/write d[5] read/write d[4] read/write d[3] reserved d[2] reserved d[1] reserved d[0] reserved low temperature limit for remote zone, least significat bits. rese rved always reads zero. bit function operation d[7:4] low temperature limit for the remote zone, least significant bits . read/write d[3:0] reserved always reads as zero power-up default value: 0000 0000 b = 00 h (0 c) read/write command byte: 0001 0100 b = 14 h each lsb represents one-sixteenth degree centigrade. the values are in a binary f ormat such that 1/16thc (0.0625c) is reported as 0001 0000b. see temperature data format for more details. any writes to a temperature limit register will result in the corresponding fault queu e being purged and reset. remote overtemperature limit register (crit1) 8-bits, read/write remote overtemperature limit register d[7] read/write d[6] read/write d[5] read/write d[4] read/write d[3] read/write d[2] read/write d[1] read/write d[0] read/write overtemperature limit for remote zone. bit function operation d[7:0] ov er temperature limit for the remote zone. read/write power-up default value: 0 11 0 0 1 00 b = 64 h ( 10 0 c) read/write command byte: 0001 1001 b = 19 h each lsb represents one degree centigrade. the values are in a twos complement binary format such that 0c is reported as 0000 0000b. see temperature data format for more details. any writes to a temperature limit register will result in the corresponding fault queu e being purged and reset. downloaded from: http:///
micrel, inc. mic280 may 5 , 20 14 24 revision 2.0 local overtemperature limit register (crit0) 8-bits, read/write local overtemperature limit register d[7] read/write d[6] read/write d[5] read/write d[4] read/write d[3] read/write d[2] read/write d[1] read/write d[0] read/write overtemperature limit for local zone. bit function operation d[7:0] overtemperature limit for the local zone. read/write power-up default value: 0100 0110 b = 46 h (70 c) read/write command byte: 0010 0000 b = 20 h each lsb represents one degree centigrade. the values are in a twos complement binary format such that 0c is reported as 0000 0000b. see temperature data format for more details. any writes to a temperature limit register will result in the corresponding fault queu e being purged and reset. manufacturer id register (mfg_id) 8-bits, read only manufacturer id register d[7] read-only d[6] r ead -only d[5] read-only d[4] read-only d[3] read-only d[2] read-only d[1] read-only d[0] read-only 0 0 1 0 1 0 1 0 bit function operation d[7:0] identifies micrel, inc. as the manufacturer of the device read only. always returns 2a h power-up default value: 0010 10 10 b = 2a h read command byte: 1111 111 0 b = fe h die revision register (die_rev) 8-bits, read only die revision register d[7] read-only d[6] read-only d[5] read-only d[4] read-only d[3] read-only d[2] read-only d[1] read-only d[0] read-only mic280 die revision number bit function operation d[7:0] identifies the device revision number. read only power-up default value: [device revision number] h read command byte: 1111 1111 b = ff h downloaded from: http:///
micrel, inc. mic280 may 5 , 20 14 25 revision 2.0 application information remote diode section most small-signal pnp transistors with characteristics similar to the jedec 2n3906 will perform well as remote temperature sensors. table 8 lists several examples of such parts that micrel has tested for use with the mic280. other transistors equivalent to these should also work well. table 8. transistors suitable for use as remote diodes vendor part number package fairchild semiconductor mmbt3906 sot- 23 on semiconductor mmbt3906l sot- 23 philips semiconductor pmbt3906 sot- 23 samsung semiconductor kst3906- tf sot- 23 minimizing errors self-heating one concern when using a part with the temperature accuracy and resolution of the mic280 is to avoid errors induced by self-heating (v dd i dd ) + (v ol i ol ). in order to understand what level of error this might represent, and how to reduce that error, the dissipation in the mic280 must be calculated and its effects reduced to a temperature offset. the worst-case operating condition for the mic280 is when v dd = 3.6v. the maximum powe r dissipated in the part is given in the following equation: p d = [(i dd v dd )+(i ol(data) v ol(data) )+(i ol(/int) v ol(/int) ] p d = [(0.4ma 3.6v)+(6ma 0.5v)+(6ma 0.5v)] p d = 7.44mw r (j - a) of the sot23-6 package is 230c/w theoretical maximum ?t j due to sel f-heating is: 7.44mw 230c/w = 1.7112c in most applications, the /int output will be low for at most a few milliseconds before the host resets it back to the high state, making its duty cycle low enough that its contribution to self-heating of the mic280 is negligible. similarly, the data pin will in all likelihood have a duty cycle of substantially below 25% in the low state. these considerations, combined with more typical device and application parameters, give a better system-level view of device self-heating in interrupt-mode usage given in the following equation: (0.23ma i dd(typ) 3.3v) + (25% 1.5ma i ol(data) 0.15v) + (1% 1.5ma i ol(/int) 0.15v) = 0.817mw ?t j = (0.8175mw 230c/w) = 0.188c in any application, the best test is to verify performance against calculation in the ?nal application environment. this is especially true when dealing with systems for which tem - perature data may be poorly de?ned or unobtainable except by empirical means. series resistance the operation of the mic280 depends upon sensing the v cb -e of a diode-connected pnp transistor (diode) at two different current levels. for remote temperature measurements, this is done using an external diode connected between t1 and ground. because this technique relies upon measuring the relatively small voltage difference resulting from two levels of current through the external diode, any resistance in series with the external diode will cause an error in the temperature reading from the mic280. a good rule of thumb is that for each ohm in series with the external transistor, there will be a 0.8c error in the mic280s temperature measurement. it is not dif?cult to keep the series resistance well below an ohm (typically < 0.1 ? ), so this will rarely be an issue. filter capacitor selection it is usually desirable to employ a ?lter capacitor between the t1 and gnd pins of the mic280. the use of this capacitor is recommended in environments with a lot of high frequency noise (such as digital switching noise), or if long wires are used to conect to the remote diode. the maximum recom- mended total capacitance from the t1 pin to gnd is 2200pf. this typically suggests the use of a 1800pf np0 or c0g ceramic capacitor with a 10% tolerance. if the remote diode is to be at a distance of more than six- to -twelve inches from the mic280, using twisted pair wiring or shielded microphone cable for the connections to the diode can signi?cantly reduce noise pickup. if using a long run of shielded cable, remember to subtract the cable's conductor- to -shield capacitance from the 2200pf maximum total capacitance. layout considerations the following guidelines should be kept in mind when designing and laying out circuits using the mic280. 1. place the mic280 as close to the remote diode as possible, while taking care to avoid severe noise sources such as high frequency power transformers, crts, memory and data busses, and the like. 2. because any conductance from the various voltages on the pc board and the t1 line can induce serious errors, it is good practice to guard the remote diode's emitter trace with a pair of ground traces. these ground traces should be returned to the mic280's own ground pin. they should not be grounded at any other part of their run. however, it is highly desirable to use these guard traces to carry the diode's own ground return back to the ground pin of the mic280, thereby downloaded from: http:///
micrel, inc. mic280 may 5 , 20 14 26 revision 2.0 providing a kelvin connection for the base of the diode. see figure 6. 3. when using the mic280 to sense the temperature of a processor or other device which has an integral thermal diode, e.g., intel's pentium ii, iii, iv, amd athlon cpu, xilinx virtex fpgas, connect the emitter and base of the remote sensor to the mic280 using the guard traces and kelvin return shown in figure 6. the collector of the remote diode is typically inaccessible to the user on these devices. to allow for this, the mic280 has superb rejection of noise appearing from collector to gnd. 4. due to the small currents involved in the measurement of the remote diodes ?v be , it is important to adequately clean the pc board after soldering to prevent current leakage. this is most likely to show up as an issue in situations where water-soluble soldering ?uxes are used. 5. in general, wider traces for the ground and t1 lines will help reduce susceptibility to radiated noise (wider traces are less inductive). use trace widths and spacing of 10mm wherever possible and provide a ground plane under the mic280 and under the connections from the mic280 to the remote diode. this will help guard against stray noise pickup. 6. always place a good quality power supply bypass capacitor directly adjacent to, or underneath, the mic280. this should be a 0.1 f ceramic capacitor. surface-mount parts provide the best bypassing because of their low inductance. 7. when the mic280 is being powered from particularly noisy power supplies, or from supplies which may have sudden high-amplitude spikes appearing on them, it can be helpful to add additional power supply ?ltering. this should be implemented as a 100 resistor in series with the parts vdd pin, and a 4.7f, 6.3v electrolytic capacitor from vdd to gnd. see figure 7. figure 6. guard traces/kelvin ground returns figure 7. vdd decoupling for very noisy supplies downloaded from: http:///
micrel, inc. mic280 may 5 , 20 14 27 revision 2.0 package information ( 21 ) 6-pin sot23 ( m6 ) note: 21. package information is correct as of the publication dat e. for updates and most current information, go to www.micrel.com . downloaded from: http:///
micrel, inc. mic280 may 5 , 20 14 28 revision 2.0 micrel, inc. 2180 fortune drive san jose, ca 95131 usa tel +1 (408) 944-0800 fax +1 (408) 474-1000 web http://www.micrel.com micrel makes no representations or warranties with respect to the accuracy or completeness of the information furn ished in this data sheet. this information is not intended as a warranty and micrel does n ot assume responsibility for its use. micrel reserves th e right to change circuitry, specifications and descriptions at any time without notice . no license, whether express, implied, arising by est oppel or otherwise, to any intellectual property rights is granted by this document. except as provided in micrels terms and conditions of sale for such products, micrel assumes no liability whatsoever, and micrel disclaims any express or implied warra nty relating to the sale and/or use of micrel products includ ing liability or warranties relating to fitness for a particular purpose, merchantability , or infringement of any patent, copyright or other intelle ctual property right. micrel products are not designed or authorized for use a s components in life support appliances, devices or syst ems where malfunction of a product can reasonably be expected to result in personal injury. l ife support devices or systems are devices or systems t hat (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. a purchasers use or sale of micrel products for use in li fe support appliances, devices or systems is a purcha sers o wn risk and purchaser agrees to fully indemnify micrel for any damages resulting from such use or sale. ? 20 14 micrel, incorporated. downloaded from: http:///

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