LM84 NSC | Alldatasheet
Document overview
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Technical content
Features
n Directly senses die temperature of remote ICs n Senses temperature of remote diodes n SMBus compatible interface, supports SMBus Timeout n Register readback capability n 7 bit plus sign temperature data format n 2 address select lines enable 9 LM84s to be connected to a single bus Key Specifications j Supply Voltage 3.0V - 3.6V j Supply Current 1 mA (max) j Local Temperature Accuracy ±1.0˚C (typ) j Remote Diode Temperature Accuracy +60˚C to +100˚C ±3˚C (max) 0˚C to +125˚C ±5˚C (max)
Applications
n System Thermal Management n Personal Computers n Electronic Test Equipment n Office Electronics n HVAC Simplified Block Diagram SMBus ™ is a trademark of the Intel Corporation. Pentium® II processor is a registered trademark of the Intel Corporation. I2C ® is a registered trademark of the Philips Corporation. DS100961-1 # Indicates Active Low (”NOT“) July 2000 LM84 Diode Input Digital Temperature Sensor with Two-Wire Interface © 2001 National Semiconductor Corporation DS100961 www.national.com
Ordering Information
(QSOP-16)
95 Units in
1.1 20MHz LM84BIMQAX MQA16A (QSOP-16)
2500 Units on
1.1 20MHz LM84CIMQA MQA16A (QSOP-16)
1.0 Not Available
(QSOP-16) www.national.com 2
Label Pin # Function Typical Connection NC 1, 5, 9, 13, 16 Manufacturing test pins. Left floating. PC board traces may be routed through the pads for these pins. Although, the components that drive these traces should share the same supply as the LM84 so that the Absolute Maximum Voltage at any Pin rating is not violated. V CC 2 Positive Supply Voltage Input DC Voltage from 3.0V to 3.6V D+ 3 Diode Current Source To Diode Anode. Connected to remote discrete diode or to the diode on the external IC whose die temperature is being sensed. D− 4 Diode Return Current Sink To Diode Cathode. Must be grounded when not used. ADD0–ADD1 10, 6 User-Set SMBus (I 2C) Address Inputs Ground (Low, “0”), VCC (High, “1”) or open (“TRI-LEVEL”) GND 7, 8 Power Supply Ground Ground T_CRIT_A 11 Critical Temperature Alarm, open-drain output Pull Up Resistor, Controller Interrupt Line or System Shutdown SMBData 12 SMBus (I2C) Serial Bi-Directional Data Line, open-drain output From and to Controller, Pull Up Resistor SMBCLK 14 SMBus (I 2C) Clock Input From Controller NC 15 No Connection Left floating. PC board traces may be routed through the pads for this pin. LM84 www.national.com3
Absolute Maximum Ratings(Note 1) Supply Voltage −0.3V to 6.0V Voltage at Any Pin: NC (Pins 1,5,9), ADD0, ADD1, D+ −0.3V to (VCC + 0.3V) All other pins (except D−) −0.3V to 6.0V D− Input Current ±1m A Input Current at All Other Pins (Note 2) 5 mA Package Input Current (Note 2) 20 mA SMBData, T_CRIT_A Output Sink Current 10 mA Output Voltage 6.0V Storage Temperature −65˚C to +150˚C Soldering Information, Lead Temperature Vapor Phase (60 seconds) 215˚C Infrared (15 seconds) 220˚C ESD Susceptibility (Note 4) Human Body Model 2500V Machine Model 250V Operating Ratings (Note 1) and (Note 5) Specified Temperature Range T MIN to TMAX LM84 0˚C to +125˚C Supply Voltage Range (VCC ) +3.0V to +3.6V Temperature-to-Digital Converter Characteristics Unless otherwise noted, these specifications apply for VCC =+3.0 Vdc to +3.6 Vdc.Boldface limits apply for TA =T J =T MIN to TMAX ;all other limits TA =T J=+25˚C, unless otherwise noted. Parameter Conditions Typical Limits Units (Note 6) (Note 7) (Limit) Local Temperature Error (Note 8) ±1˚ C Remote Temperature Error using Pentium Diode (Note 8) and (Note +60˚C ≤T A ≤ +100˚C, VCC = 3.3 Vdc ±3 ˚C (max) 0˚C ≤ TA ≤ +125˚C, VCC = 3.3 Vdc ±5 ˚C (max) Remote Temperature Error using Diode Connected 2N3904 (Note 8) and (Note 9) +60˚C ≤T A ≤ +100˚C, VCC = 3.3 Vdc +1, −5 ˚C (max) 0˚C ≤ TA ≤ +125˚C, VCC = 3.3 Vdc +3, −7 ˚C (max) Resolution 8 Bits 1˚ C Temperature Conversion Time (Note 11) 120 145 ms Quiescent Current (Note 10) SMBus (I 2C Inactive) 0.500 1 mA (max) D− Source Voltage 0.7 V Diode Source Current (D+ − D−)=+ 0.65V; high level 160 µA (max) 50 µA (min) Low level 16 µA (max) 5 µA (min) T_CRIT_A Output Saturation Voltage IOUT = 3.0 mA 0.4 V (max) Power-On Reset Threshold On V CC input, falling edge 2.2 1.2 V (max) V (min) Local and Remote T_CRIT Default Temperature (Note 12) +127 ˚C LM84 www.national.com 4
Logic Electrical Characteristics DIGITAL DC CHARACTERISTICS Unless otherwise noted, these specifications apply for VCC =+3.0 to 3.6 Vdc.Boldface limits apply for TA =T J =T MIN to TMAX ;all other limits TA =T J=+25˚C, unless otherwise noted. Symbol Parameter Conditions Typical LM84B LM84C Units (Note 6) Limits (Note 7) Limits (Note 7) (Limit) SMBData, SMBCLK VIN(1) Logical “1” Input Voltage 2.1 1.4 V (min) VIN(0) Logical “0”Input Voltage 0.8 0.6 V (max) IIN(1) Logical “1” Input Current V IN =V CC 0.005 1.0 1.0 µA (max) IIN(0) Logical “0” Input Current V IN = 0V −0.005 −1.0 −1.0 µA (max) ADD0, ADD1 V IN(1) Logical “1” Input Voltage V CC 1.6 1.6 V (min) VIN(0) Logical “0”Input Voltage GND 0.5 0.5 V (max) IIN(1) Logical “1” Input Current V IN =V CC 50 600 600 µA (max) IIN(0) Logical “0” Input Current V IN =0 V 5 0 600 600 µA (max) ALL DIGITAL INPUTS C IN Input Capacitance 20 pF ALL DIGITAL OUTPUTS I OH High Level Output Current V OH =V CC 100 100 µA (max) VOL SMBus Low Level Output Voltage IOL =3m A IOL =6m A 0.4 0.6 0.4 0.6 V (max) LM84 www.national.com5
Logic Electrical Characteristics(Continued) SMBus DIGITAL SWITCHING CHARACTERISTICS Unless otherwise noted, these specifications apply for VCC =+3.0 Vdc to +3.6 Vdc, CL (load capacitance) on output lines = 80 pF.Boldface limits apply for TA =T J =T MIN to TMAX ;all other limits TA =T J = +25˚C, unless otherwise noted. The switching characteristics of the LM84 fully meet or exceed the published specifications of the SMBus or I2C bus. The fol- lowing parameters are the timing relationships between SMBCLK and SMBData signals related to the LM84. They are not nec- essarily the I 2C or SMBus bus specifications. Symbol Parameter Conditions Typical Limits Units (Note 6) (Note 7) (Limit) fSMB SMBus Clock Frequency 400 kHz (max) kHz (min) tLOW SMBus Clock Low Time 10% to 10% 1.3 µs (min) ms (max) tLOW SEXT Cumulative Clock Low Extend Time 25 ms (max) tHIGH SMBus Clock High Time 90% to 90% 0.6 µs (min) tR;SMB SMBus Rise Time 10% to 90% 1 µs tF;SMB SMBus Fall Time 90% to 10% 0.3 µs tOF Output Fall Time C L = 400 pF IO =3m A 250 ns (max) tTIMEOUT SMBData and SMBCLK Time Low for Reset of Serial Interface (Note 13) ms (min) ms (max) t1 SMBCLK (Clock) Period 2.5 µs (min) t2, tSU;DAT Data In Setup Time to SMBCLK High 100 ns (min) t3, tHD;DAT Data Out Stable after SMBCLK Low 0 0.9 ns (min) µs (max) t4, tHD;STA SMBData Low Setup Time to SMBCLK Low 100 ns (min) t tSU;STO SMBData High Delay Time after SMBCLK High (Stop Condition Setup) 100 ns (min) t tSU;STA SMBus Start-Condition Setup Time 0.6 µs (min) tBUF SMBus Free Time 1.3 µs (min) SMBus Communication DS100961-4 LM84 www.national.com 6
Logic Electrical Characteristics(Continued) SMBus TIMEOUT DS100961-13 LM84 www.national.com7
the device beyond its rated operating conditions. maximum package input current rating limits the number of pins that can safely exceed the power supplies with an input current of 5 mA to four. temperature or voltage measurement. Note: An x indicates that the diode exists. Semiconductor Linear Data Book for other methods of soldering surface mount devices. Note 4:Human body model, 100 pF discharged through a 1.5 kΩ resistor. Machine model, 200 pF discharged directly into each pin. Note 5:Thermal resistance of the QSOP-16 package is TBD ˚C/W, junction-to-ambient when attached to a printed circuit board with 2 oz. foil. Note 6:Typicals are at TA = 25˚C and represent most likely parametric norm. Note 7:Limits are guaranteed to National’s AOQL (Average Outgoing Quality Level). Note 8:The Temperature Error specification does not include an additional error of±1˚C, caused by the quantization error. Note 9: The Temperature Error will vary less than±1.0˚C for a variation in VCC of 3V to 3.6V from the nominal of 3.3V. Note 10:Quiescent current will not increase substantially with an active SMBus. (and will yield last conversion result). Note 12:Default values set at power up. state of an SMBus communication (SMBCLK and SMBData set High). FIGURE 1. ESD Protection Input Structure
1.0 Functional Description
1.1 T_CRIT_A OUTPUT, T_CRIT LIMITS
Figure 3. The T_CRIT_A mask bit (bit 7 of the Configuration Register) when set will disable the T_CRIT_A output. Register is read and if the temperature is below the setpoint.
1.2 POWER-ON RESET DEFAULT STATES
- Local Temperature set to 0˚C
- Remote Temperature set to 0˚C until the LM84 senses a
- Status Register set to 00h.
- Command Register set to 00h; T_CRIT_A enabled.
- Local and Remote T_CRIT set to 127˚C
FIGURE 2. Temperature-to-Digital Transfer Function (Non-linear scale for clarity) FIGURE 3. T_CRIT_A Temperature Response Diagram
1.0 Functional Description(Continued)
1.3 SMBus INTERFACE
The LM84 operates as a slave on the SMBus, so the SMBCLK line is an input (no clock is generated by the LM84) and the SMBData line is bi-directional. According to SMBus specifications, the LM84 has a 7-bit slave address. Bit 4 (A3) of the slave address is hard wired inside the LM84 to a 1. The remainder of the address bits are controlled by the address select pins ADD1 and ADD0, and are set by con- necting these pins to ground for a low, (0) , to V CC for a high, (1), or left floating (TRI-LEVEL). Therefore, the complete slave address is: A6 A5 A4 A3 A2 A1 A0 MSB LSB and is selected as follows: Address Select Pin State LM84 SMBus Slave Address ADD0 ADD1 A6:A0 binary 0 0 001 1000
0 TRI-LEVEL 001 1001
TRI-LEVEL TRI-LEVEL 010 1010 TRI-LEVEL 1 010 1011 1 0 100 1100
1 TRI-LEVEL 100 1101
The LM84 latches the state of the address select pins during the first read or write on the SMBus. Changing the state of the address select pins after the first read or write to any device on the SMBus will not change the slave address of the LM84.
1.4 TEMPERATURE DATA FORMAT
Temperature data can be read from the Local Temperature, Remote Temperature, and T_CRIT setpoint registers. Tem- perature data can only be written to the T_CRIT setpoint registers. Temperature data is represented by an 8-bit, two’s complement byte with an LSB (Least Significant Bit) equal to 1˚C: Temperature Digital Output Binary Hex +125˚C 0111 1101 7Dh +25˚C 0001 1001 19h +1˚C 0000 0001 01h 0˚C 0000 0000 00h −1˚C 1111 1111 FFh −25˚C 1110 0111 E7h −55˚C 1100 1001 C9h
1.5 OPEN-DRAIN OUTPUTS
SMBData and T_CRIT_A outputs are open-drain and do not have internal pull-ups. A “high” level will not be observed on these pins until pull-up current is provided from some exter- nal source, typically a pull-up resistor. Choice of resistor value depends on many system factors but, in general, the pull-up resistor should be as large as possible. This will minimize any local temperature reading errors due to self heating of the LM84. The maximum resistance of the pull-up, based on LM84 specification for High Level Output Current, to provide a 2V high level, is 30 kΩ .
1.6 DIODE FAULT DETECTION
Before each remote conversion the LM84 goes through an external diode fault detection sequence. If the D+ input is shorted to V CC or floating then the temperature reading will be +127˚C, bit 2 (OPEN) of the Status Register will be set. If the Remote T_CRIT setpoint is set to less than +127˚C then bit 4 (RTCRIT) of the Status Register will be set which will activate the T_CRIT_A output, if enabled. If D+ is shorted to GND or D−, the temperature reading will be 0˚C and bit 2 of the Status Register will not be set. LM84 www.national.com 10
1.7 COMMUNICATING with the LM84
There are 10 data registers in the LM84, selected by the Command Register. At power-up the Command Register is set to “00”, the location for the Read Local Temperature Register. The Command Register latches whatever the last location it was set to. Reading the Status Register resets T_CRIT_A. All registers are predefined as read only or write only. Read and write registers with the same function contain mirrored data. A Writeto the LM84 will always include the address byte and the command byte. A write to any register requires one data byte. Reading the LM84 can take place either of two ways: 1. If the location latched in the Command Register is cor- rect (most of the time it is expected that the Command Register will point to one of the Read Temperature Reg- isters because that will be the data most frequently read from the LM84), the read can simply consist of an ad- dress byte, followed by retrieving the data byte. 2. If the Command Register needs to be set, then an address byte, command byte, repeat start, and another address byte will accomplish a read. The data byte has the most significant bit first. At the end of a read, the LM84 can accept either Acknowledge or No Acknowledge from the Master (No Acknowledge is typically used as a signal for the slave that the Master has read its last byte).
1.7.1 SMBus TIMEOUT
The LM84 SMBus interface circuitry will be reset to the SMBus idle state if the SMBData or SMBCLK lines are held low for more than 40 ms. The LM84 may or may not reset the state SMBData or SMBCLK if either of these lines are held low between 25 ms and 40 ms. Holding SMBData or SMB- CLK low for less than or equal to 25 ms will not reset the interface circuitry. The LM84 has a built-in internal timer to guarantee that the interface is reset if the SMBData line were to get stuck low. This can commonly occur when the master is reset while the slave is transmitting low. This enhance- ment to the SMBus TIMEOUT specification ensures error free performance even in remote systems where complete power supply shutdown, for reset, is a nuisance. This would have to occur since many cost effective temperature sensors such as the LM84 do not have a pin dedicated for reset. DS100961-9 LM84 www.national.com11
1.8 LM84 REGISTERS
1.8.1 COMMAND REGISTER
Selects which registers will be read from or written to. Data for this register should be transmitted during the Command Byte of the SMBus write communication. P7 P6 P5 P4 P3 P2 P1 P0
0000 Command Select
P0-P7: Command Select: Command Se- lect Address Power On Default State Register Name Register Function <P7:P0> hex <D7:D0 > binary <D7:D0 > deci- mal 00h 0000 0000 0 RLT Read Local Temperature 01h 0000 0000 0 RRT Read Remote Temperature 02h 0000 0000 0 RS Read Status 03h 0000 0000 0 RC Read Configuration 04h 0000 0000 0 RMID Manufacturers ID 05h 0111 1111 127 RLCS Read Local T_CRIT Setpoint 07h 0111 1111 127 RRCS Read Remote T_CRIT Setpoint 09h 0000 0000 0 WC Write Configuration 0Bh 0111 1111 127 WLCS Write Local T_CRIT Setpoint 0Dh 0111 1111 127 WRCS Write Remote T_CRIT Setpoint
1.8.2 LOCAL and REMOTE TEMPERATURE REGISTERS
(Read Only Address 00h and 01h): D7 D6 D5 D4 D3 D2 D1 D0 MSB Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 LSB D7–D0: Temperature Data. One LSB = 1˚C. Two’s complement format.
1.8.3 STATUS REGISTER
(Read Only Address 02h): D7 D6 D5 D4 D3 D2 D1 D0
0 LTCRIT 0 RTCRIT 0 OPEN 0 0
Power up default is with all bits “0” (zero). D2: OPEN: When set to 1 indicates a Remote Diode disconnect. D4: RTCRIT: When set to 1 indicates an RT_CRIT alarm. D6: LTCRIT: When set to 1 indicates an LT_CRIT alarm. D7, D5, D3, D1–D0: These bits are always set to 0.
1.8.4 Manufacturers ID Register
(Read Address 04h) Default value 00h.
1.8.5 CONFIGURATION REGISTER
(Read Address 03h /Write Address 09h): D7 D6 D5 D4 D3 D2 D1 D0 T_CRIT_A mask 0000000 Power up default is with all bits “0” (zero). D7: T_CRIT_A mask: When set to 1 T_CRIT_A interrupts are masked. D6–D0: These bits are always set to 0. A write of 1 will return a 0 when read. LM84 www.national.com 12
1.8.6 LOCAL AND REMOTE T_CRIT REGISTERS
D7–D0: RT_CRIT and LT_CRIT setpoint temperature data. Power up default is LT_CRIT = RT_CRIT = 127˚C.
2.0 SMBus Timing Diagrams
(c) Serial Bus Read from a Register with the internal Command Register preset to desired value. FIGURE 4. Serial Bus Timing Diagrams
3.0 Application Hints
sensing capability allows it to be used in new ways as well. circuit board lands and traces soldered to the LM84’s pins. more strongly than will the air temperature. Figure 5. A discrete diode can also be
3.1 ACCURACY EFFECTS OF DIODE NON-IDEALITY
- η is the non-ideality factor of the process the diode is manufactured on,
- q is the electron charge,
- k is the Boltzmann’s constant,
- N is the current ratio,
- T is the absolute temperature in ˚K. The temperature sensor then measuresΔVBE and converts to digital data. In this equation, k and q are well defined universal constants, and N is a parameter controlled by the temperature sensor. The only other parameter isη, which depends on the diode that is used for measurement. Since ΔV BE is proportional to bothη and T, the variations inη cannot be distinguished from variations in temperature. Since the non-ideality factor is not controlled by the tempera- ture sensor, it will directly add to the inaccuracy of the sensor. For the Pentium II Intel specifies a ±1% variation in η from part to part. As an example, assume a temperature sensor has an accuracy specification of±3˚C at room tem- perature of 25˚C and the process used to manufacture the diode has a non-ideality variation of ±1%. The resulting accuracy of the temperature sensor at room temperature will be: T The additional inaccuracy in the temperature measurement caused byη, can be eliminated if each temperature sensor is calibrated with the remote diode that it will be paired with.
3.2 PCB LAYOUT for MINIMIZING NOISE
sor and the LM84 can cause temperature conversion errors.
- Place a 0.1 µF power supply bypass capacitor as close
capacitor as close as possible to the D+ and D− pins.
- Ideally, the LM84 should be placed within 10 cm of the
short and identical as possible.
- Diode traces should be surrounded by a GND guard ring
- Avoid routing diode traces in close proximity to power
supply switching or filtering inductors.
- Avoid running diode traces close to or parallel to high
at least 2 cm. apart from the high speed digital traces.
- If it is necessary to cross high speed digital traces, the
3.0 Application Hints(Continued)
- The ideal place to connect the LM84’s GND pin is as
4.0 Typical Applications
FIGURE 6. Recommended Diode Trace Layout
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