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| MIC384 Micrel MIC384 Three-Zone Thermal Supervisor Advance Information General Description The MIC384 is a versatile digital thermal supervisor capable of measuring temperature using its own internal sensor and two inexpensive external sensors or embedded silicon diodes such as those found in the Intel Pentium III* CPU. A 2wire serial interface is provided to allow communication with either I2C** or SMBus* masters. The open-drain interrupt output pin can be used as either an over-temperature alarm or a thermostatic control signal. Interrupt mask and status bits are provided for reduced software overhead. Fault queues prevent nuisance tripping due to thermal or electrical noise. A programmable address pin permits two devices to share the bus. (Alternate base addresses available - contact Micrel.) Superior performance, low power and small size makes the MIC384 an excellent choice for multiple zone thermal management applications. *SMBus and Pentium III are trademarks of Intel Corporation. **I2C is a trademark of Philips Electronics, N.V. Features * * * * * * * * * * * * * * * Measures Local and Two Remote Temperatures 2-Wire SMBus-compatible Interface Programmable Thermostat Settings for All Three Zones Open-Drain Interrupt Output Pin Interrupt Mask and Status Bits Fault Queues to Prevent Nuisance Tripping Low Power Shutdown Mode Failsafe response to diode faults 2.7V to 5.5V Power Supply Range 8-Lead SOIC and MSOP Packages Desktop, Server and Notebook Computers Power Supplies Test and Measurement Equipment Wireless Systems Networking/Datacom Hardware Applications Ordering Information Part Number MIC384-0BM MIC384-1BM MIC384-2BM MIC384-3BM MIC384-0BMM MIC384-1BMM MIC384-2BMM MIC384-3BMM Base Address(*) 100 100x 100 101x 100 110x 100 111x 100 100x 100 101x 100 110x 100 111x Junction Temp. Range -55C to +125C -55C to +125C -55C to +125C -55C to +125C -55C to +125C -55C to +125C -55C to +125C -55C to +125C Package 8-Lead SOP 8-Lead SOP 8-Lead SOP 8-Lead SOP 8-Lead MSOP 8-Lead MSOP 8-Lead MSOP 8-Lead MSOP Contact Factory Contact Factory Contact Factory Contact Factory Contact Factory Contact Factory Notes * The least-significant bit of the slave address is determined by the state of the A0 pin. Typical Application 3.3V 3 x 10k pull-ups FROM SERIAL BUS HOST 0.1F MIC384 DATA VDD CLK T1 /INT GND T2 A0 2200pF REMOTE DIODE REMOTE DIODE 2200pF 3-Channel SMBus Temperature Measurement System Micrel, Inc. * 1849 Fortune Drive * San Jose, CA 95131 * USA * tel + 1 (408) 944-0800 * fax + 1 (408) 944-0970 * http://www.micrel.com September 2000 1 MIC384 MIC384 Micrel Pin Configuration DATA 1 CLK 2 /INT 3 GND 4 8 VDD 7 A0 6 T1 5 T2 Pin Description Pin Number 1 2 3 4 5 6 7 8 Pin Name DATA CLK /INT GND T2 T1 A0 VDD Pin Function Digital I/O: Open-drain. Serial data input/output. Digital Input: The host provides the serial bit clock on this input. Digital Output: Open-drain. Interrupt or thermostat output. Ground: Power and signal return for all IC functions. Analog Input: Connection to remote temperature sensor (diode junction) Analog Input: Connection to remote temperature sensor (diode junction) Digital Input: Slave address selection input. See Table 1. MIC284 Slave Address Setings. Analog Input: Power supply input to the IC. MIC384 2 September 2000 MIC384 Micrel Absolute Maximum Ratings (Note 1) Power Supply Voltage, VDD ................................................... 6.0V Voltage on Any Pin ................................ -0.3V to VDD+0.3V Current Into Any Pin ................................................. 10mA Power Dissipation, TA = +125C ............................... 30mW Junction Temperature ............................................. +150C Storage Temperature ............................... -65C to +150C ESD Ratings (Note 3) Human Body Model .................................................. TBD V Machine Model ......................................................... TBD V Soldering Vapor Phase (60 sec.) ............................. +220C +5-0C Infrared (15 sec.) ...................................... +235C +5-0C Operating Ratings (Note 2) Power Supply Voltage, VDD .............................. +2.7V to +5.5V Ambient Temperature Range (TA) ............ -55C to +125C Package Thermal Resistance (JA) SOP .................................................................+152C/W MSOP .............................................................. +206C/W Electrical Characteristics 2.7V VDD 5.5; TA = +25C, bold values indicate -55C TA +125C, Note 4; unless noted. Symbol Power Supply IDD Supply Current /INT, open, A0 = VDD or GND, CLK = DATA = high, normal mode /INT, open, A0 = VDD or GND, shutdown mode, CLK = 100kHz /INT, open, A0 = VDD or GND, shutdown mode, CLK = DATA = high tPOR VPOR VHYST Power-On Reset Time; Note 7 Power-On Reset Voltage Power-On Reset Hysteresis Voltage 0C TA +100C, /INT open, 3V VDD 3.6V -55C TA +125C, /INT open, 3V VDD 3.6V Accuracy--Remote Temperature Note 5, 4, 9 0C TD +100C, /INT open, 3V VDD 3.6V, 0C TA +85C -55C TD +125C, /INT open, 3V VDD 3.6V, 0C TA +85C tCONV0 tCONV1 Conversion Time, local zone Note 7, 8 Conversion Time, remote zone Note 7, 8 VDD > VPOR all registers reset to default values, A/D conversions initiated 2.0 250 1 2 1 2 50 350 3 1 10 200 2.7 750 A A A s V mV Parameter Condition Min Typ Max Units Temperature-to-Digital Converter Characteristics Accuracy--Local Temperature Note 4, 9 2 3 3 5 80 C C C C ms 100 160 ms A A Remote Temperature Inputs (T1, T2) IF Current to External Diode Note 7 high level, T1 or T2 forced to 1.5V low level 2.7V VDD 5.5V 2.7V VDD 5.5V 2.0 10 0.01 7.5 224 14 400 Address Input (A0) VIL VIH CIN ILEAK Low Input Voltage High Input Voltage Input Capacitance Input Current 0.6 V V pF 1 A September 2000 3 MIC384 MIC384 Symbol Parameter Condition Min Typ Max Micrel Units Serial Data I/O Pin (DATA) VOL VIL VIH CIN ILEAK VIL VIH CIN ILEAK VOL tINT tnINT T_SET0 T_HYST0 T_SET1 T_HYST1 T_SET2 T_HYST2 Low Output Voltage Note 6 Low Input Voltage High Input Voltage Input Capacitance Input current 2.7V VDD 5.5V 2.7V VDD 5.5V 0.7VDD 10 0.01 IOL = 3mA IOL = 6mA 2.7V VDD 5.5V 2.7V VDD 5.5V 0.7VDD 10 0.01 0.4 0.8 0.3VDD V V V V pF 1 0.3VDD A Serial Clock Input (CLK) Low Input Voltage High Input Voltage Input Capacitance Input current V V pF 1 0.4 0.8 tCONV+1 1 A Status Output (/INT) Low Output Voltage, Note 6 Interrupt Propagation Delay, Note 7, 8 Interrupt Reset Propagation Delay, Note 7 Default T_SET0 Value Default T_HYST0 Value Default T_SET1 Value Default T_HYST1 Value Default T_SET2 Value Default T_HYST2 Value IOL = 3mA IOL = 6mA from TEMPx > T_SETx or TEMPx < T_HYSTx to /INT < VOL, FQ = 00, RPULLUP = 10k from any register read to /INT > VOH, RPULLUP = 10k tPOR after VDD > VPOR tPOR after VDD > VPOR tPOR after VDD > VPOR tPOR after VDD > VPOR tPOR after VDD > VPOR tPOR after VDD > VPOR 81 76 97 92 97 92 81 76 97 92 97 92 V V s s C C C C C C s ns ns ns ns 81 76 97 92 97 92 Serial Interface Timing (Note 7) t1 t2 t3 t4 t5 Note 1. Note 2. Note 3. Note 4. Note 5. Note 6. Note 7. Note 8. CLK (Clock) Period Data In Setup Time to CLK High Data Out Stable After CLK Low DATA Low Setup Time to CLK Low DATA High Hold Time After CLK High start condition stop condition 2.5 100 0 100 100 Exceeding the absolute maximum rating may damage the device. The device is not guaranteed to function outside its operating rating. Devices are ESD sensitive. Handling precautions recommended. Human body model: 1.5k in series with 100pF. Machine model: 200pF, no series resistance. Final test on outgoing product is performed at TA = TBDC. TD is the temperature of the remote diode junction. Testing is performed using a single unit of one of the transistors listed in Table 6. Current into this pin will result in self-heating of the MIC384. Sink current should be minimized for best accuracy. Guaranteed by design over the operating temperature range. Not 100% production tested. tCONV = tCONV0 +(2 X tCONV1). tCONV0 is the conversion time for the local zone; tCONV1 is the conversion time for the remote zones. MIC384 4 September 2000 MIC384 Note 9. Accuracy specification does not include quantization noise, which may be as great as 12LSB (0.5C). Micrel Timing Diagram t1 SCL t4 SDA Data In t3 SDA Data Out t2 t5 Serial Interface Timing September 2000 5 MIC384 MIC384 Micrel Functional Diagram VDD 8-Bit Sigma-Delta ADC T1 T2 3:1 MUX Digital Filter and Control Logic Bandgap Sensor and Reference 1-Bit DAC Result Registers A0 2-Wire Serial Bus Interface DATA CLK Pointer Register Temperature Setpoint Registers Temperature Hysteresis Registers State Machine and Digital Comparator Configuration Register Open-Drain Output MIC384 GND /INT Functional Description Pin Descriptions VDD: Power supply input. See electrical specifications. GND: Ground return for all MIC384 functions. CLK: Clock input to the MIC384 from the two-wire serial bus. The clock signal is provided by the host, and is shared by all devices on the bus. DATA: Serial data I/O pin that connects to the two-wire serial bus. DATA is bi-directional and has an open-drain output driver. An external pull-up resistor or current source somewhere in the system is necessary on this line. This line is shared by all devices on the bus. A0: This inputs sets the least significant bit of the MIC384's 7-bit slave address. The six most-significant bits are fixed and are determined by the part number ordered. (See ordering information table above.) Each MIC384 will only respond to its own unique slave address, allowing up to eight MIC384's to share a single bus. A match between the MIC384's address and the address specified in the serial bit stream must be made to initiate communication. A0 should be tied directly to VDD or ground. See "Temperature Measurement and Power On" for more information. A0 determines the slave address as shown in Table 1: Part Number MIC384-0 MIC384-1 MIC384-2 MIC384-3 Inputs A0 0 1 0 1 0 1 0 1 MIC384 Slave Address Binary 100 1000b 100 1001b 100 1010b 100 1011b 100 1100b 100 1101b 100 1110b 100 1111b Hex 48h 49h 4Ah 4Bh 4Ch 4Dh 4Eh 4Fh Table 1. MIC384 Slave Address Settings /INT: Temperature events are indicated to external circuitry via this output. Operation of the /INT output is controlled by the MODE and IM bits in the MIC384's configuration register. See "Comparator and Interrupt Modes" below. This output is open-drain and may be wire-OR'ed with other open-drain signals. Most systems will require a pull-up resistor or current source on this pin. If the IM bit in the configuration register is 6 September 2000 MIC384 MIC384 set, it prevents the /INT output from sinking current. In I2C and SMBus systems, the IM bit is therefore an interrupt mask bit. T1 and T2: The T1 and T2 pins connect to off-chip PN diode junctions, for monitoring the temperature at remote locations. The remote diodes may be embedded thermal sensing junctions in integrated circuits so equipped (such as Intel's Pentium III), or discrete 2N3906-type bipolar transistors with base and collector tied together. Temperature Measurement The temperature-to-digital converter is built around a switched current source and an eight-bit analog-to-digital converter. The temperature is calculated by measuring the forward voltage of a diode junction at two different bias current levels. An internal multiplexer directs the current source's output to either the internal or one of the external diode junctions. The MIC384 uses two's-complement data to represent temperatures. If the MSB of a temperature value is zero, the temperature is zero or positive. If the MSB is one, the temperature is negative. More detail on this is given in the "Temperature Data Format" section below. A "temperature event" results if the value in any of the temperature result registers (TEMPx) becomes greater than the value in the corresponding temperature setpoint register (T_SETx). Another temperature event occurs if and when the measured temperature subsequently falls below the temperature hysteresis setting in T_HYSTx. During normal operation the MIC384 continuously performs temperature-to-digital conversions, compares the results against the setpoint and hysteresis registers, and updates the state of /INT and the status bits accordingly. The remote zones are converted first, followed by the local zone (T1T2LOCAL). The states of /INT and the status bits are updated after each measurement is taken. Diode Faults The MIC384 is designed to respond in a failsafe manner to hardware faults in the external sensing circuitry. If the connection to an external diode is lost or the sense line (T1 or T2) is shorted to VDD or ground, the temperature data reported by the A/D converter will be forced to its full-scale value (+127C). This will cause a temperature event to occur if the setpoint register for the corresponding zone is set to any Micrel value less than 127C (7Fh = 0111 1111b). An interrupt will be generated on /INT if so enabled. The temperature reported for the external zone will remain +127C until the fault condition is cleared. This fault detection mechanism requires that the MIC384 complete the number of conversion cycles specified by Fault_Queue (see below). The part will therefore require one or more conversion cycles following power-on or a transition from shutdown to normal operation before reporting an external diode fault. Serial Port Operation The MIC384 uses standard SMBus Write_Byte and Read_Byte operations for communication with its host. The SMBus Write_Byte operation involves sending the device's slave address (with the R/W bit low to signal a write operation), followed by a command byte and a data byte. The SMBus Read_Byte operation is similar, but is a composite write and read operation: the host first sends the device's slave address followed by the command byte, as in a write operation. A new start bit must then be sent to the MIC384, 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. The command byte is eight bits wide. This byte carries the address of the MIC384 register to be operated upon, and is stored in the part's pointer register. The pointer register is an internal write-only register. The command byte (pointer register) values corresponding to the various MIC384 registers are shown in Table 2. Command byte values other than those explicitly shown are reserved, and should not be used. Any command byte sent to the MIC384 will persist in the pointer register indefinitely until it is overwritten by another command byte. If the location latched in the pointer register from the last operation is known to be correct (i.e., points to the desired register), then the Receive_Byte procedure may be used. To perform a Receive_Byte, the host sends an address byte to select the MIC384, and then retrieves the data byte. Figures 1 through 3 show the formats for these procedures. Command_Byte Binary 0000 0000b 0000 0001b 0000 0010b 0000 0011b 0001 0000b 0001 0010b 0001 0011b 0010 0000b 0010 0010b 0010 0011b Hex 00h 01h 02h 03h 10h 12h 13h 20h 22h 23h Label TEMP0 CONFIG T_HYST0 T_SET0 TEMP1 T_SET1 TEMP2 T_HYST2 T_SET2 Target Register Description local temperature configuration register local temperature hysteresis local temperature setpoint remote zone 1 temperature remote zone 1 temperature setpoint remote zone 2 temperature remote zone 2 temperature hysteresis remote zone 2 temperature setpoint T_HYST1 remote zone 1 temperature hysteresis Table 2. MIC384 Register Addresses September 2000 7 MIC384 MIC384 MIC384 MIC384 Slave Address Command Byte Data Byte to MIC384 DATA S 1 0 0 1 X X A0 0 A 0 0 X X X X X X A X X X X X X X X /A P START STOP R/W = WRITE ACKNOWLEDGE ACKNOWLEDGE NOT ACKNOWLEDGE CLK Master-to-slave transmission Slave-to-master response Figure 1. WRITE_BYTE Protocol MIC384 Slave Address Command Byte MIC384 Slave Address Data Read From MIC384 DATA S 1 0 0 1 X X A0 0 A 0 0 X X X X X X A S 1 0 0 1 X X A0 1 A X X X X X X X X /A P R/W = WRITE ACKNOWLEDGE ACKNOWLEDGE START R/W = READ ACKNOWLEDGE NOT ACKNOWLEDGE STOP START 8 CLK Master-to-slave transmission Slave-to-master response Figure 2. READ_BYTE Protocol MIC384 Slave Address Data Byte from MIC384 DATA S 1 0 0 1 X X A0 1 A X X X X X X X X /A P START R/W = READ ACKNOWLEDGE NOT ACKNOWLEDGE STOP CLK Master-to-slave transmission Slave-to-master response Figure 3. RECEIVE_BYTE Micrel September 2000 MIC384 September 2000 First Byte of Transaction Last Byte of Transaction ... X X X X X X X X /A P NOT ACKNOWLEDGE STOP R/W = DONT CARE ACKNOWLEDGE ACKNOWLEDGE MIC384 Slave Address S1001XXXXAXXXXXXXXA Conversion in Progress A/D Converter in Standby New Conversion Begins Slave-to-master response Conversion Interrupted By MIC384 Acknowledge Master-to-slave transmission START New Conversion in Progress tCONV1 First Result Ready Figure 4. A/D Converter Timing 9 MIC384 Slave Address Command Byte = 01h = CONFIG MIC384 Slave Address CONFIG Value* START R/W = WRITE ACKNOWLEDGE ACKNOWLEDGE START R/W = READ ACKNOWLEDGE NOT ACKNOWLEDGE STOP S 1 0 0 0 X X A0 0 A 0 0 0 0 0 0 0 1 A S 1 0 0 0 X X A0 1 A X X X X X X X X /A P tn/INT t/INT INT Temperature event occurs * Status bits in CONFIG are cleared to zero following this operation Master-to-slave transmission Slave-to-master response Figure 5. Responding to Interrupts MIC384 Micrel MIC384 Temperature Data Format The LSB of each register represents one degree Centigrade. The values are in a two's complement format, wherein the most significant bit (D7) represents the sign: zero for positive temperatures and one for negative temperatures. Table 3 shows examples of the data format used by the MIC384 for temperatures. A/D Converter Timing Whenever the MIC384 is not in its low power shutdown mode, the internal A/D converter (ADC) attempts to make continuous conversions unless interrupted by a bus transaction accessing the MIC384. Upon powering up or coming out of shutdown mode, the ADC will begin acquiring temperature data starting with the first external zone, zone 1, then the second external zone, zone 2, and finally the internal zone, zone 0. Results for zone 1 will be valid after tCONV1, results for zone two will be ready after another tCONV1, and for the local zone tCONV0 later. Figure 4 shows this behavior. The conversion time is twice as long for external conversions as it is for internal conversions. This allws the use of a filter capacitor on T1 and/or T2 without a loss of accuracy due to the resulting longer settling times. Upon powering up, coming out of shutdown mode, or resuming operation following a serial bus transaction, the ADC will begin aquiring temperature data with the first external zone (zone 1), followed by the second external zone (zone 2), and then the internal zone (zone 0). If the ADC in interrupted by a serial bus transaction, it will restart the conversion that was interrupted and then continue in the normal sequence. This sequence will repeat indefinitely until the MIC384 is shut down, powered off, or is interrupted by a serial bus transaction as described above. Power On When power is initially applied, the MIC384's internal registers are set to their default states. Also at this time, the level on the address input, A0, is read to establish the device's slave address. The MIC384's power-up default state can be summarized as follows: * Normal mode operation (i.e., part is not in shutdown) * /INT function is set to comparator mode * Fault queue depth = 1 (FQ=00) * Interrupts are enabled (IM = 0) * T_SET0 = 81C; T_HYST0 = 76C * T_SET1 = 97C; T_HYST1 = 92C * T_SET2 = 97C; T_HYST2 = 92C * Initialized to recognize overtemperature faults Micrel Comparator and Interrupt Modes Depending on the setting of the MODE bit in the configuration register, the /INT output will behave either as an interrupt request signal or a thermostatic control signal. Thermostatic operation is known as comparator mode. The /INT output is asserted when the measured temperature, as reported in any of the TEMPx registers, exceeds the threshold programmed into the corresponding T_SETx register for the number of conversions specified by Fault_Queue (described below). In comparator mode, /INT will remain asserted and the status bit(s) will remain high unless and until the measured temperature falls below the value in the T_HYSTx register for Fault_Queue conversions. No action on the part of the host is required for operation in comparator mode. Note that entering shutdown mode will not affect the state of /INT when the device is in comparator mode. In interrupt mode, once a temperature event has caused a status bit to be set and the /INT output to be asserted, they will not be automatically de-asserted when the measured temperature falls below T_HYSTx. They can only be de-asserted by reading any of the MIC384's internal registers or by putting the device into shutdown mode. If the most recent temperature event was an overtemperature condition, Sx will not be set again, and /INT cannot be reasserted, until the device has detected that TEMPx < T_HYSTx. Similarly, if the most recent temperature event was an undertemperature condition, Sx will not be set again, and /INT cannot be reasserted, until the device has detected that TEMPx > T_SETx. This keeps the internal logic of the MIC384 backward compatible with that of the LM75 and similar devices. In both modes, the MIC384 will be responsive to over-temperature events at power-up. See "Interrupt Generation", below. Shutdown Mode Setting the SHDN bit in the configuration register halts the otherwise continuous conversions by the A/D converter. The MIC384's power consumption drops to 1A typical in shutdown mode. All registers may be read from or written to while in shutdown mode. Serial bus activity will slightly increase the part's power consumption. Entering shutdown mode will not affect the state of /INT when the device is in comparator mode (MODE = 0). It will retain its state until after the device exits shutdown mode and resumes A/D conversions. However, if the device is shut down while in interrupt mode, the /INT pin will be unconditionally de-asserted and the internal latches holding the interrupt status will be cleared. Therefore, no interrupts will be generated while the MIC384 MIC384 10 September 2000 MIC384 Micrel Temperature +125 C +100 C +25 C +1.0 C 0 C - 1.0 C - 25 C - 40 C - 55 C Binary 0111 1101b 0110 0100b 0001 1001b 0000 0001b 0000 0000b 1111 1111b 1110 0111b 1101 1000b 1100 1001b Hex 7Dh 64h 19h 01h 00h FFh E7h D8h C9h Table 3. Digital Temperature Format September 2000 11 MIC384 MIC384 is in shutdown mode, and the interrupt status will not be retained. Since entering shutdown mode stops A/D conversions, the MIC384 is incapable of detecting or reporting temperature events of any kind while in shutdown. Diode faults require one or more A/D conversion cycles to be recognized, and therefore will not be reported either while the device is in shutdown (see "Diode Faults" above). Fault_Queue Fault queues (programmable digital filters) are provided in the MIC384 to prevent false tripping due to thermal or electrical noise. The two bits in CONFIG[4:3] set the depth of Fault_Queue. Fault_Queue then determines the number of consecutive temperature events (TEMPx > T_SETx, or TEMPx < T_HYSTx) which must occur in order for the condition to be considered valid. There are separate fault queues for each zone. As an example, assume the part is in comparator mode, and CONFIG[4:3] is programmed with 10b. The measured temperature in zone one would have to exceed T_SET1 for four consecutive A/D conversions before /INT would be asserted or the S1 status bit set. Similarly, TEMP1 would then have to be less than T_HYST1 for four consecutive conversions before /INT would be reset. Like any filter, the fault queue function also has the effect of delaying the detection of temperature events. In this example, it would take 4 x tCONV to detect a temperature event. The depth of Fault_Queue vs. D[4:3] of the configuration register is shown in Table 4. CONFIG[4:3] 00 01 10 11 * Default setting Micrel CONFIG and assert its /INT output. These conditions are listed in Table 5. When a temperature event occurs, the corresponding status bit will be set in CONFIG. This action cannot be masked. However, a temperature event will only generate an interrupt signal on /INT if it is specifically enabled by the interrupt mask bit (IM =0 in CONFIG). Following an interrupt, the host should read the contents of the configuration register to confirm that the MIC384 was the source of the interrupt. A read operation on any register will cause /INT to be de-asserted. This is shown in Figure 5. The status bits will only be cleared once CONFIG has been read. Since temperature-to-digital conversions continue while /INT is asserted, the measured temperature could change between the MIC384's assertion of /INT and the host's response. It is good practice for the interrupt service routine to read the value in TEMPx, to verify that the over-temperature or under-temperature 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 MIC384 by the host. The interrupt service routine should allow for this eventuality. Keep in mind that clearing the status bits and deasserting /INT is not sufficient to allow further interrupts to occur. TEMPx must become less than T_HYSTx if the last event was an over-temperature condition, or greater than T_SETx if the last event was an under-temperature condition, before /INT can be asserted again. Putting the device into shutdown mode will de-assert /INT and clear the status bits (S0, S1, and S2). This should not be done before completing the appropriate interrupt service routine(s). Polling The MIC384 may either be polled by the host, or request the host's attention via the /INT pin. In the case of polled operation, the host periodically reads the contents of CONFIG to check the state of the status bits. The act of reading CONFIG clears the status bits. If more than one event that sets a given status bit occurs before the host polls the MIC384, only the fact that at least one such event has occurred will be apparent to the host. For polled systems, the interrupt mask bit should be set (IM = 1). This will disable interrupts from the MIC384 and prevent the /INT pin from sinking current. Fault_Queue Depth 1 conversion* 2 conversions 4 conversions 6 conversions Table 4. Fault_Queue Depth Settings Interrupt Generation Assuming the MIC384 is in interrupt mode and interrupts are enabled, there are seven different conditions that will cause the MIC384 to set one of the status bits, S0, S1, or S2, in MIC384 12 September 2000 MIC384 Micrel Event high temperature, local high temperature, remote zone 1 high temperature, remote zone 2 low temperature, local low temperature, remote zone 1 low temperature, remote zone 2 diode fault Condition* TEMP0 > T_SET0 TEMP1 > T_SET1 TEMP1 > T_SET2 TEMP0 < T_HYST0 TEMP1 < T_HYST1 TEMP1 < T_HYST2 T1 or T2 open or shorted to VDD or GND MIC284 response** set S0 in CONFIG, assert /INT set S1 in CONFIG, assert /INT set S2 in CONFIG, assert /INT set S0 in CONFIG, assert /INT set S1 in CONFIG, assert /INT set S2 in CONFIG, assert /INT set CRIT and S1 and/or S2 in CONFIG, assert /INT and /CRIT*** * Condition must be true for FAULT_QUEUE conversion to be recognized ** Assumes interrupts are enabled *** Assumes that T_SET1 and T_SET2 are set to any value less then +127 C = 7fh = 0111 1111b Table 5. MIC384 Temperature Events September 2000 13 MIC384 MIC384 Micrel Register Set and Programmer's Model Internal Register Set Name TEMP0 CONFIG T_HYST0 T_SET0 TEMP1 T_HYST1 T_SET1 TEMP2 T_HYST2 T_SET2 (1) (2) Description measured temperature, local zone configuration register hysteresis setting, local zone temperature setpoint, local zone measured temperature, zone 1 hysteresis setting, zone 1 temperature setpoint, zone 1 measured temperature, zone 2 hysteresis setting, zone 2 temperature setpoint, zone 2 Command Byte 00h 01h 02h 03h 10h 12 h 13h 20h 22h 23h Operation 8-bit read only 8-bit read/write 8-bit read/write 8-bit read/write 8-bit read only 8-bit read/write 8-bit read/write 8-bit read only 8-bit read/write 8-bit read/write Power-Up Default 00h (0 C)(1) 00h(2) 4Ch (+76 C) 51h (+81 C) 00h (0 C)(1) 5Ch (+92 C) 61h (+97 C) 00h (0 C)(1) 5Ch (+92 C) 61h (+97 C) TEMPx will contain measured temperature data after the completion of one conversion cycle. After the first Fault_Queue conversions are complete, status bits will be set if TEMPx > T_SETx. Detailed Register Descriptions Configuration Register CONFIGURATION REGISTER (CONFIG) 8-Bit Read/Write D[7] read only zone 0 status (S0) D[6] read only zone 1 status (S1) D[5] read only zone 2 status (S2) D[4] D[3] D[2] read/write interrupt mask (IM) D[1] read/write CMP/INT mode (MODE) D[0] read/write Shutdown (SHDN) read/write fault queue depth (FQ[1:0]) Bits S0 S1 S2 Function local interrupt status (read only) remote zone 1 interrupt status (read only) remote zone 2 interrupt status (read only) Operation 1 = event occured, 0 = no event 1 = event occured, 0 = no event 1 = event occured, 0 = no event 00 = 1 conversion, 01 = 2 conversions, 10 = 4 conversions, 11 = 6 conversions 1 = disabled, 0 = interrupts enabled 1 = interrupt mode, 0 = comparator mode 1 = shutdown, 0 = normal FQ[1:0] Fault_Queue depth IM MODE SHDN interrupt mask comparator/interrupt mode selection for /INT pin normal/shutdown operating mode selection CONFIG Power-Up Value: 0000 0000b = 00h(*) * not in shutdown mode * comparator mode * Fault_Queue depth = 1 * interrupts enabled. * no temperature events pending CONFIG Command Byte Value: 0000 0001b = 01h * Following the first Fault_Queue conversions, one or more of the status bits may be set. MIC384 14 September 2000 MIC384 Local Temperature Result Register LOCAL TEMPERATURE RESULTS (TEMP0) 8-Bit Read Only D[7] MSB D[6] bit 6 D[5] bit 5 D[4] bit 4 D[3] bit 3 D[2] bit 2 D[1] bit 1 D[0] LSB Micrel local temperature data from ADC* Bits D[7:0] Function measured temperature data for the local zone* read only Operation TEMP0 Power-Up Value: 0000 0000b = 00h (0C) TEMP0 Command Byte Value: 0000 0000b = 00h * Each LSB represents one degree Centigrade. The values are in a two's complement format such that 0C is reported as 0000 0000b. See "Temperature Data Format" for more details. TEMP0 will contain measured temperature data after the completion of one conversion. Local Hysteresis Register LOCAL TEMPERATURE HYSTERESIS (T_HYST0) 8-Bit Read/Write D[7] MSB D[6] bit 6 D[5] bit 5 D[4] bit 4 D[3] bit 3 D[2] bit 2 D[1] bit 1 D[0] LSB local temperature hysteresis setting Bits D[7:0] Function local temperature hysteresis setting* read/write Operation T_HYST0 Power-Up Value: 0100 1100b = 4Ch (+76C) T_HYST0 Command Byte Value: 0000 0010b = 02h * Each LSB represents one degree Centigrade. The values are in a two's complement format such that 0C is reported as 0000 0000b. See "Temperature Data Format" for more details. Local Temperature Setpoint Register LOCAL TEMPERATURE SETPOINT (T_SET0) 8-Bit Read/Write D[7] MSB D[6] bit 6 D[5] bit 5 D[4] bit 4 D[3] bit 3 D[2] bit 2 D[1] bit 1 D[0] LSB local temperature setpoint Bits D[7:0] Function local temperature setpoint* read/write Operation T_SET0 Power-Up Value: 0101 0001b = 51h (+81C) T_SET0 Command Byte Value: 0000 0011b = 03h * Each LSB represents one degree Centigrade. The values are in a two's complement format such that 0C is reported as 0000 0000b. See "Temperature Data Format" for more details. September 2000 15 MIC384 MIC384 Remote Zone 1 Temperature Result Register REMOTE ZONE 1 TEMPERATURE RESULT (TEMP1) 8-Bit Read Only D[7] MSB D[6] bit 6 D[5] bit 5 D[4] bit 4 D[3] bit 3 D[2] bit 2 D[1] bit 1 D[0] LSB Micrel remote zone 1 temperature data from ADC* Bits D[7:0] Function measured temperature data for remote zone one* read only Operation TEMP1 Power-Up Value: 0000 0000b = 00h (0C) TEMP1 Command Byte Value: 0001 0000b = 10h * Each LSB represents one degree Centigrade. The values are in a two's complement format such that 0C is reported as 0000 0000b. See "Temperature Data Format" for more details. TEMP1 will contain measured temperature data for the selected zone after the completion of one conversion. Remote Zone 1 Hysteresis Register REMOTE ZONE 1 TEMPERATURE HYSTERESIS REGISTER (T_HYST1) 8-Bit Read/Write D[7] MSB D[6] bit 6 D[5] bit 5 D[4] bit 4 D[3] bit 3 D[2] bit 2 D[1] bit 1 D[0] LSB remote zone 1 temperature hysteresis* Bits D[7:0] Function remote zone one temperature hysteresis* read/write Operation T_HYST1 Power-Up Value: 0101 1100b = 5Ch (+92C) T_HYST1 Command Byte Value: 0001 0010b = 12h * Each LSB represents one degree Centigrade. The values are in a two's complement format such that 0C is reported as 0000 0000b. See "Temperature Data Format" for more details. Remote Zone 1 Temperature Setpoint Register REMOTE ZONE 1 TEMPERATURE SETPOINT (T_SET1) 8-Bit Read/Write D[7] MSB D[6] bit 6 D[5] bit 5 D[4] bit 4 D[3] bit 3 D[2] bit 2 D[1] bit 1 D[0] LSB remote zone 1 temperature setpoint Bits D[7:0] Function remote zone one temperature setpoint* read/write Operation T_SET1 Power-Up Value: 0110 0001b = 61h (+97C) T_SET1 Command Byte Value: 0001 0011b = 13h * Each LSB represents one degree Centigrade. The values are in a two's complement format such that 0C is reported as 0000 0000b. See "Temperature Data Format" for more details. MIC384 16 September 2000 MIC384 Remote Zone 2 Temperature Result Register REMOTE ZONE 2 TEMPERATURE RESULTS REGISTER (TEMP2) 8-Bit Read Only D[7] MSB D[6] bit 6 D[5] bit 5 D[4] bit 4 D[3] bit 3 D[2] bit 2 D[1] bit 1 D[0] LSB Micrel remote zone 2 temperature data from ADC* Bits D[7:0] Function measured temperature data for remote zone 2* read only Operation TEMP2 Power-Up Value: 0000 0000b = 00h (0C) TEMP2 Command Byte Value: 0010 0000b = 20h * Each LSB represents one degree Centigrade. The values are in a two's complement format such that 0C is reported as 0000 0000b. See "Temperature Data Format" for more details. TEMP2 will contain measured temperature data for the selected zone after the completion of one conversion. Remote Zone 2 Hysteresis Register REMOTE ZONE 2 HYSTERESIS REGISTER (T_HYST2) 8-Bit Read/Write D[7] MSB D[6] bit 6 D[5] bit 5 D[4] bit 4 D[3] bit 3 D[2] bit 2 D[1] bit 1 D[0] LSB remote zone 2 temperature hysteresis setting Bits D[7:0] Function remote zone 2 temperature hysteresis setting* read/write Operation T_HYST2 Power-Up Value: 0101 1100b = 5Ch (+92C) T_HYST2 Command Byte Value: 0010 0010b = 22h * Each LSB represents one degree Centigrade. The values are in a two's complement format such that 0C is reported as 0000 0000b. See "Temperature Data Format" for more details. Remote Zone 2 Setpoint Register REMOTE ZONE 2 TEMPERATURE SETPOINT (T_SET2) 8-Bit Read/Write D[7] MSB D[6] bit 6 D[5] bit 5 D[4] bit 4 D[3] bit 3 D[2] bit 2 D[1] bit 1 D[0] LSB remote zone 2 temperature setpoint Bits D[7:0] Function remote zone 2 temperature setpoint* read/write Operation T_SET2 Power-Up Value: 0110 0001b = 61h (+97C) T_SET2 Command Byte Value: 0010 0011b = 23h * Each LSB represents one degree Centigrade. The values are in a two's complement format such that 0C is reported as 0000 0000b. See "Temperature Data Format" for more details. September 2000 17 MIC384 MIC384 Micrel In any application, the best test is to verify performance against calculation in the final application environment. This is especially true when dealing with systems for which some of the thermal data (e.g., PC board thermal conductivity and ambient temperature) may be poorly defined or unobtainable except by empirical means. Series resistance The operation of the MIC384 depends upon sensing the VCB-E of a diode-connected PNP transistor ("diode") at two different current levels. For remote temperature measurements, this is done using external diodes connected between T1, T2 and ground. Since this technique relies upon measuring the relatively small voltage difference resulting from two levels of current through the external diodes, any resistance in series with those diodes will cause an error in the temperature reading from the MIC384. A good rule of thumb is this: for each ohm in series with a zone's external transistor, there will be a 0.9C error in the MIC384's temperature measurement. It isn't difficult to keep the series resistance well below an ohm (typically < 0.1), so this will rarely be an issue. Filter capacitor selection It is sometimes desirable to use a filter capacitor between the T1 and/or T2 pins and the GND pin of the MIC384. The use of these capacitors is recommended in environments with a lot of high frequency noise (such as digital switching noise), or if long wires are used to attach to the remote diodes. The maximum recommended total capacitance from the T1 or T2 pin to GND is 2700pF. This typically suggests the use of 2200pF NP0 or C0G ceramic capacitors with a 10% tolerance. If a remote diode is to be at a distance of more than 6"--12" from the MIC384, using twisted pair wiring or shielded microphone cable for the connections to the diode can significantly help reduce noise pickup. If using a long run of shielded cable, remember to subtract the cable's conductor-to-shield capacitance from the 2700pF maximum total capacitance. Applications Remote Diode Selection Most small-signal PNP transistors with characteristics similar to the JEDEC 2N3906 will perform well as remote temperature sensors. Table 6 lists several examples of such parts that Micrel has tested for use with the MIC384. Other transistors equivalent to these should also work well. Minimizing Errors Self-Heating One concern when using a part with the temperature accuracy and resolution of the MIC384 is to avoid errors in measuring the local temperature induced by self-heating. Self-heating is caused by the power naturally dissipated inside the device due to operating supply current and I/O sink currents (VDD x IDD ) + (VOL x IOL). In order to understand what level of error this represents, and how to reduce that error, the dissipation in the MIC384 must be calculated and its effects reduced to a temperature offset. The worst-case operating condition for the MIC384 is when VDD = 5.5V, MSOP-08 package. The maximum power dissipated in the part is given in Equation 1 below. 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 MIC384 is negligible. Similarly, the DATA pin will in all likelihood have a duty cycle of substantially less than 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 interruptmode. This is illustrated in Equation 2. If the part is to be used in comparator mode, calculations similar to those shown above (accounting for the expected value and duty cycle of IOL(INT)) will give a good estimate of the temperature error due to self-heating. PD = [(IDD x VDD ) + (IOL(DATA) ) + (IOL(/INT) x VOL(/INT) )] PD = [(0.75mA x 5.5V) + (6mA x 0.8V) + (6mA x 0.8V)] PD = 13.73mW R q(j - a) of MSOP - 08 package is 206C / W Maximum TJ relative to TA due to self - heating is 13.73mW x 206C / W = 2.83C Equation 1. Worst-Case Self-Heating [(0.350mA IDD(typ) x 3.3V) + (25% x 1.5mA IOL(DATA) x 0.3V) + (1% x 1.5mA IOL(/INT) x 0.3V)] = 1.27mW TJ = (1.27mW x 206C / W) TJ = 0.262C Equation 2. Real-World Self-heating Example Vendor Fairchild On Semiconductor Phillips Semiconductor Samsung Part Number MMBT3906 MMBT3906L PMBT3906 KST3906-TF Package SOT-23 SOT-23 SOT-23 SOT-23 Table 6. Transistors Suitable for Remote Temperature Sensing Use MIC384 18 September 2000 MIC384 Layout Considerations The following guidelines should be kept in mind when designing and laying out circuits using the MIC384: 1. Place the MIC384 as close to the remote diodes 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. Since any conductance from the various voltages on the PC Board to the T1 or T2 line can induce serious errors, it is good practice to guard the remote diodes' emitter traces with pairs of ground traces. These ground traces should be returned to the MIC384'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 diodes' own ground return back to the ground pin of the MIC384, thereby providing a Kelvin connection for the base of the diodes. See Figure 6. 3. When using the MIC384 to sense the temperature of a processor or other device which has an integral thermal diode, e.g., Intel's Pentium III, connect the emitter and base of the remote sensor to the MIC384 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 MIC384 has superb rejection of noise appearing from collector to GND, as long as the base to ground connection is relatively quiet. Micrel 4. Due to the small currents involved in the measurement of the remote diode's VBE, 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 fluxes are used. 5. In general, wider traces for the ground and T1/ T2 lines will help reduce susceptibility to radiated noise (wider traces are less inductive). Use trace widths and spacing of 10 mils wherever possible and provide a ground plane under the MIC384 and under the connections from the MIC384 to the remote diodes. This will help guard against stray noise pickup. 6. Always place a good quality 0.1F power supply bypass capacitor directly adjacent to, or underneath, the MIC384. Surface-mount capacitors are preferable because of their low inductance. 7. When the MIC384 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 filtering. This should be implemented as a 100 resistor in series with the part's VDD pin, and an additional 4.7F, 6.3V electrolytic capacitor from VDD to GND. See Figure 7. MIC384 1 DATA 2 CLK 3 /INT 4 GND VDD 8 A0 7 T1 6 T2 5 GUARD/RETURN REMOTE DIODE (T1) GUARD/RETURN GUARD/RETURN REMOTE DIODE (T2) GUARD/RETURN Figure 6. Guard Traces/Kelvin Ground Returns September 2000 19 MIC384 MIC384 Micrel 3.3V 10k pull-ups FROM SERIAL BUS HOST 100 0.1F MIC384 DATA VDD CLK T1 / INT T2 GND A0 4.7F Remote Diode 2200pF Remote Diode 2200pF Figure 7. VDD Decoupling for Very Noisy Supplies MIC384 20 September 2000 MIC384 Micrel Package Information 0.026 (0.65) MAX) PIN 1 0.157 (3.99) 0.150 (3.81) DIMENSIONS: INCHES (MM) 0.050 (1.27) TYP 0.020 (0.51) 0.013 (0.33) 0.0098 (0.249) 0.0040 (0.102) 0-8 SEATING PLANE 45 0.010 (0.25) 0.007 (0.18) 0.064 (1.63) 0.045 (1.14) 0.197 (5.0) 0.189 (4.8) 0.050 (1.27) 0.016 (0.40) 0.244 (6.20) 0.228 (5.79) 8-Lead SOP (M) 0.122 (3.10) 0.112 (2.84) 0.199 (5.05) 0.187 (4.74) DIMENSIONS: INCH (MM) 0.120 (3.05) 0.116 (2.95) 0.036 (0.90) 0.032 (0.81) 0.043 (1.09) 0.038 (0.97) 0.012 (0.30) R 0.007 (0.18) 0.005 (0.13) 0.012 (0.03) 0.0256 (0.65) TYP 0.008 (0.20) 0.004 (0.10) 5 MAX 0 MIN 0.012 (0.03) R 0.039 (0.99) 0.035 (0.89) 0.021 (0.53) 8-Lead MSOP (MM) MICREL INC. TEL 1849 FORTUNE DRIVE SAN JOSE, CA 95131 FAX USA + 1 (408) 944-0800 + 1 (408) 944-0970 WEB http://www.micrel.com This information is believed to be accurate and reliable, however no responsibility is assumed by Micrel for its use nor for any infringement of patents or other rights of third parties resulting from its use. No license is granted by implication or otherwise under any patent or patent right of Micrel Inc. (c) 2000 Micrel Incorporated September 2000 21 MIC384 |
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