LM77 NSC | Alldatasheet
Document overview
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Technical content
Features
n Window comparison simplifies design of ACPI compatible temperature monitoring and control. n Serial Bus interface n Separate open-drain outputs for Interrupt and Critical Temperature shutdown n Shutdown mode to minimize power consumption n Up to 4 LM77s can be connected to a single bus n 9-bit + sign output; full-scale reading of over 128˚C n SOP and MSOP 8-lead packages Key Specifications j Supply Voltage 3.0V to 5.5V j Supply Current operating 250 µA (typ) 500 µA (max) shutdown 5 µA (typ) j Temperature Accuracy −10˚C to 65˚C ±1.5˚C(max)
Applications
n System Thermal Management n Personal Computers n Office Electronics n Electronic Test Equipment n Automotive n HVAC I2C ® is a registered trademark of Philips Corporation. July 2001 LM77 9-Bit + Sign Digital Temperature Sensor and Thermal Window Comparator with Two-Wire Interface © 2001 National Semiconductor Corporation DS100136 www.national.com
Ordering Information
Order Number Supply Voltage Package Supplied In LM77CIM-3 3.3V SOP8, M08A Rail LM77CIMX-3 3.3V SOP8, M08A 2500 Units on Tape and Reel LM77CIM-5 5V SOP8, M08A Rail LM77CIMX-5 5V SOP8, M08A 2500 Units on Tape and Reel LM77CIMM-3 3.3V MSOP8, MUA08A Rail LM77CIMMX-3 3.3V MSOP8, MUA08A
3500 Units on Tape and Reel
LM77CIMM-5 5V MSOP8, MUA08A Rail LM77CIMMX-5 5V MSOP8, MUA08A Label Pin # Function Typical Connection SDA 1 Serial Bi-Directional Data Line. Open Drain Output From Controller SCL 2 Serial Bus Clock Input From Controller T_CRIT_A 3 Critical Temperature Alarm Open Drain Output Pull Up Resistor, Controller Interrupt Line or System Hardware Shutdown GND 4 Power Supply Ground Ground INT 5 Interrupt Open Drain Output Pull Up Resistor, Controller Interrupt Line S 8 Positive Supply Voltage Input DC Voltage from 3V to 5.5V A0–A1 7,6 User-Set Address Inputs Ground (Low, “0”) or +V S (High, “1”) DS100136-1 SOP8 or MSOP DS100136-2 LM77 See NS Package Number M08A or MM08A LM77 www.national.com 2
FIGURE 1. Typical Application
Absolute Maximum Ratings(Note 1) Supply Voltage −0.3V to 6.5V Voltage at any Pin −0.3V to (+V S + 0.3V ) Input Current at any Pin 5 mA Package Input Current (Note 2) 20 mA T_CRIT_A and INT Output Sink Current 10 mA T_CRIT_A and INT Output Voltage 6.5V Storage Temperature −65˚C to +125˚C Soldering Information, Lead Temperature SOP and MSOP Package (Note 3) Vapor Phase (60 seconds) 215˚C Infrared (15 seconds) 220˚C ESD Susceptibility (Note 4) Human Body Model 2500V Machine Model 250V Operating Ratings(Notes 1, 5) Specified Temperature Range T MIN to TMAX (Note 6) −55˚C to +125˚C Supply Voltage Range (+VS)(Note 7) +3.0V to +5.5V Temperature-to-Digital Converter Characteristics Unless otherwise noted, these specifications apply for +VS =+5 Vdc ±10% for LM77CIM-5, LM77CIMM-5 and +VS =+3.3 Vdc ±10% for LM77CIM-3, LM77CIMM-3 (Note 7).Boldface limits apply for TA =T J =T MIN to TMAX ;all other limits TA = TJ=+25˚C, unless otherwise noted. Parameter Conditions Typical (Note 8) Limits (Note 9) Units (Limit) Accuracy T A = −10˚C to +65˚C ±1.5 ˚C (max)TA = −25˚C to +100˚C ±2.0 Resolution (Note 10) 10 0.5 Bits Temperature Conversion Time (Note 11) 70 125 ms Quiescent Current I 2C Inactive 0.25 mA I2C Active 0.25 0.5 mA (max) Shutdown Mode 5 10 µA THYST Default Temperature (Notes 13, 14) 2 ˚C TLOW Default Temperature (Note 14) 10 ˚C THIGH Default Temperature (Note 14) 64 ˚C TC Default Temperature (Note 14) 80 ˚C Logic Electrical Characteristics DIGITAL DC CHARACTERISTICS Unless otherwise noted, these specifications apply for +VS =+5 Vdc ±10% for LM77CIM-5, LM77CIMM-5 and +V S =+3.3 Vdc±10% for LM77CIM-3, LM77CIMM-3.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 (Note 8) Limits (Note 9) Units (Limit) VIN(1) SDA and SCL Logical “1” Input Voltage +V S x 0.7 V (min) +V S+0.3 V (max) VIN(0) SDA and SCL Logical “0” Input Voltage −0.3 V (min) +V S x 0.3 V (max) VIN(1) A0 and A1 Logical “1” Input Voltage
2.0 V (min)
+V S+0.3 V (max) VIN(0) A0 and A1 Logical “0” Input Voltage −0.3 V (min)
0.8 V (max)
IIN(1) Logical “1” Input Current V IN =+V S 0.005 1.0 µA (max) IIN(0) Logical “0” Input Current V IN = 0V −0.005 −1.0 µA (max) C IN Capacitance of All Digital Inputs 20 pF LM77 www.national.com 4
Logic Electrical Characteristics(Continued) DIGITAL DC CHARACTERISTICS Unless otherwise noted, these specifications apply for +VS =+5 Vdc ±10% for LM77CIM-5, LM77CIMM-5 and +V S =+3.3 Vdc±10% for LM77CIM-3, LM77CIMM-3.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 (Note 8) Limits (Note 9) Units (Limit) IOH High Level Output Current V OH =+V S 10 µA (max) VOL Low Level Output Voltage I OL =3m A 0.4 V (max) T_CRIT_A Output Saturation Voltage IOUT = 4.0 mA (Note 12) T_CRIT_A Delay 1 Conversions (max) tOF Output Fall Time C L = 400 pF 250 ns (max) IO =3m A LM77 www.national.com5
Logic Electrical Characteristics(Continued) SERIAL BUS DIGITAL SWITCHING CHARACTERISTICS Unless otherwise noted, these specifications apply for +VS =+5 Vdc ±10% for LM77CIM-5 and LM77CIMM-5, +VS =+3.3 Vdc±10% for LM77CIM-3 and LM77CIMM-3, CL (load capacitance) on output lines = 80 pF unless otherwise specified. 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 LM77 fully meet or exceed the published specifications of the I 2C bus. The following pa- rameters are the timing relationship between SCL and SDA signal related to the LM77. They are not the I2C bus specifications. Symbol Parameter Conditions Typical (Note 8) Limits (Note 9) Units (Limit) t1 SCL (Clock) Period 2.5 µs(min) t2 Data in Set-Up Time to SCL High 100 ns(min) t3 Data Out Stable after SCL Low 0 ns(min) t4 SDA Low Set-Up Time to SCL Low (Start Condition) 100 ns(min) t5 SDA High Hold Time after SCL High (Stop Condition) 100 ns(min) Note 1:Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. DC and AC electrical specifications do not apply when operating the device beyond its rated operating conditions. Note 2:When the input voltage (VI) at any pin exceeds the power supplies (VI< GND or VI> +V S) the current at that pin should be limited to 5 mA. The 20 mA 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. Note 3:See AN-450 “Surface Mounting Methods and Their Effect on Product Reliability” or the section titled “Surface Mount” found in a current National 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:LM77 θJA (thermal resistance, junction-to-ambient) when attached to a printed circuit board with 2 oz. foil is: 200˚C/W for the SOP-8 (M08A) package, 250˚C/W for the MSOP-8 (MUA08A) package. Note 6: While the LM77 has a full-scale-range in excess of 128˚C, prolonged operation at temperatures above 125˚C is not recommended. Note 7:Both part numbers of the LM77 will operate properly over the +VS supply voltage range of 3V to 5.5V . The devices are tested and specified for rated accuracy at their nominal supply voltage. Accuracy will typically degrade 1˚C/V of variation in +VS as it varies from the nominal value. Note 8: Typicals are at TA = 25˚C and represent most likely parametric norm. Note 9:Limits are guaranteed to National’s AOQL (Average Outgoing Quality Level). Note 10:9 bits + sign, two’s complement Note 11:This specification is provided only to indicate how often temperature data is updated. The LM77 can be read at any time without regard to conversion state (and will yield last conversion result). If a conversion is in process it will be interrupted and restarted after the end of the read. Note 12:For best accuracy, minimize output loading. Higher sink currents can affect sensor accuracy with internal heating. This can cause an error of 0.64˚C at full rated sink current and saturation voltage based on junction-to-ambient thermal resistance. Note 13:Hysteresis value adds to the TLOW setpoint value (e.g.: if TLOW setpoint = 10˚C, and hysteresis = 2˚C, then actual hysteresis point is 10+2 = 12˚C); and subtracts from the THIGH and T_CRIT setpoints (e.g.: if THIGH setpoint = 64˚C, and hysteresis = 2˚C, then actual hysteresis point is 64−2 = 62˚C). For a detailed discussion of the function of hysteresis refer toSection 1.1, TEMPERATURE COMPARISON, and Figure 3. Note 14: Default values set at power up. DS100136-4 LM77 www.national.com 6
1.0 Functional Description
grammable for mode and polarity.
1.1 TEMPERATURE COMPARISON
1.1.1 STATUS BITS
actions, and always represent the state of temperature vs.
1.1.2 HARDWIRE OUTPUTS
condition is true, it is set again. If not, it remains reset.
- Transitioning upward across a setpoint, or
- Transitioning downward across a setpoint’s correspond-
ing hysteresis (after having exceeded that setpoint). stay that way forever if a user never read the part. However if the user read the part, the output would be reset. FIGURE 2. Temperature-to-Digital Transfer Function (Non-linear scale for clarity)
1.0 Functional Description(Continued)
terrupts just after reprogramming setpoints. Typically, sys- tem Interrupt inputs are masked prior to reprogramming trip points. By doing a read just after resetting trip points, but prior to unmasking, unexpected Interrupts are prevented. Avoid programming setpoints so close that their hysteresis values overlap. An example would be that with a T HYST value of 2˚C then setting THIGH and TLOW to within 4˚C of each other will violate this restriction. To be more specific, with T HYST set to 2˚C assume THIGH set to 64˚C. If TLOW is set equal to, or higher than 60˚C this restriction is violated.
1.2 DEFAULT SETTINGS
The LM77 always powers up in a known state. LM77 power up default conditions are: 1. Comparator Interrupt Mode 2. T LOW set to 10˚C 3. T HIGH set to 64˚C 4. T_CRIT set to 80˚C 5. T HYST set to 2˚C 6. INT and T_CRIT_A active low 7. Pointer set to “00”; Temperature Register The LM77 registers will always reset to these default values when the power supply voltage is brought up from zero volts as the supply crosses the voltage level plotted in the follow- ing curve. The LM77 registers will reset again when the power supply drops below the voltage plotted in this curve.
1.3 SERIAL BUS INTERFACE
The LM77 operates as a slave on the Serial Bus, so the SCL line is an input (no clock is generated by the LM77) and the SDA line is a bi-directional serial data line. According to Serial Bus specifications, the LM77 has a 7-bit slave ad- dress. The five most significant bits of the slave address are hard wired inside the LM77 and are “10010”. The two least significant bits of the address are assigned to pins A1–A0, and are set by connecting these pins to ground for a low, (0); or to +V S for a high, (1). Therefore, the complete slave address is:
10010 A 1 A 0
Average Power on Reset Voltage vs Temperature DS100136-18 LM77 www.national.com 8
1.4 TEMPERATURE DATA FORMAT
1.5 SHUTDOWN MODE
respond to the shutdown command.
1.6 INT AND T_CRIT_A OUTPUT
will minimize any errors due to internal heating of the LM77. volt high level, is 30K ohms.
1.7 FAULT QUEUE
Note:Event Interrupt mode is drawn as if the user is reading the part. If the user doesn’t read, the outputs would go low and stay that way until the LM77 is read. FIGURE 3. Temperature Response Diagram
1.8 INTERNAL REGISTER STRUCTURE
registers require two data bytes. required number of data bytes will accomplish a read. Figure 4. This can prevent any “Stop” condition will reset the LM77. FIGURE 4. Inadvertent 8-Bit Read from 16-Bit Register where D7 is Zero (“0”)
1.9 POINTER REGISTER
(Selects which registers will be read from or written to): P7 P6 P5 P4 P3 P2 P1 P0
00000 Register Select
P0–P2: Register Select: P2 P1 P0 Register 0 0 0 Temperature (Read only) (Power-up default) 0 0 1 Configuration (Read/Write) 010 T HYST (Read/Write) 0 1 1 T_CRIT (Read/Write) 100 T LOW (Read/Write)
101 T HIGH (Read/Write)
P3–P7: Must be kept zero.
1.10 TEMPERATURE REGISTER
(Read Only): D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 Sign Sign Sign Sign MSB Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 CRIT HIGH LOW Status Bits D0–D2: Status Bits D3–D15: Temperature Data. One LSB = 0.5˚C. Two’s complement format.
1.11 CONFIGURATION REGISTER
(Read/Write): D7 D6 D5 D4 D3 D2 D1 D0 0 0 0 Fault Queue INT Polarity T_CRIT_A Polarity INT Mode Shutdown D0: Shutdown - When set to 1 the LM77 goes to low power shutdown mode. Power up default of “0”. D1: Interrupt mode-0i s Comparator Interrupt mode, 1 is Event Interrupt mode. Power up default of “0”. D2, D3: T_CRIT_A and INT Polarity-0i sactive low, 1 is active high. Outputs are open-drain. Power up default of “0” D4: Fault Queue - When set to 1 the Fault Queu is enabled, see Section 1.7. Power up default of “0”. D5–D7: These bits are used for production testing and must be kept zero for normal operation.
1.12 THYST ,TLOW ,THIGH AND T_CRIT_A REGISTERS
(Read/Write): D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 Sign Sign Sign Sign MSB Bit7 Bit6 Bit5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 X X X D0–D2: Undefined D3–D15: THYST ,TLOW ,THIGH or T_CRIT Trip Temperature Data. Power up default is TLOW = 10˚C, THIGH = 64˚C, T_CRIT = 80˚C, THYST = 2˚C. THYST is subtracted from THIGH , and T_CRIT, and added to TLOW . Avoid programming setpoints so close that their hysteresis values overlap. SeeSection 1.1. LM77 www.national.com11
2.0 I2C Timing Diagrams
FIGURE 6. Timing Diagrams
3.0 Application Hints
The temperature response graph inFigure 7depicts a typi- cal application designed to meet ACPI requirements. In this type of application, the temperature scale is given an arbi- trary value of″granularity″, or the window within which tem- perature notification events should occur. The LM77 can be programmed to the window size chosen by the designer, and will issue interrupts to the processor whenever the window limits have been crossed. The internal flags permit quick determination of whether the temperature is rising or falling. The T_CRIT limit would typically use its separate output to activate hardware shutdown circuitry separate from the pro- cessor. This is done because it is expected that if tempera- ture has gotten this high that the processor may not be responding. The separate circuitry can then shut down the system, usually by shutting down the power supply. Note that the INT and T_CRIT_A outputs are separate, but can be wire-or’d together. Alternatively the T_CRIT_A can be diode or’d to the INT line in such a way that a T_CRIT_A event activates the INT line, but an INT event does not activate the T_CRIT_A line. This may be useful in the event that it is desirable to notify both the processor and separate T_CRIT_A shutdown circuitry of a critical temperature alarm at the same time (maybe the processor is still working and can coordinate a graceful shutdown with the separate shut- down circuit). To implement ACPI compatible sensing it is necessary to sense whenever the temperature goes outside the window, issue an interrupt, service the interrupt, and reprogram the window according to the desired granularity of the tempera- ture scale. The reprogrammed window will now have the current temperature inside it, ready to issue an interrupt whenever the temperature deviates from the current window. To understand this graph, assume that at the left hand side the system is at some nominal temperature. For the 1st event temperature rises above the upper window limit, T HIGH , causing INT to go active. The system responds to the interrupt by querying the LM77’s status bits and determines that T HIGH was exceeded, indicating that temperature is rising. The system then reprograms the temperature limits to a value higher by an amount equal to the desired granularity. Note that in Event Interrupt Mode, reprogramming the limits has caused a second, known, interrupt to be issued since temperature has been returned within the window. In Com- parator Interrupt Mode, the LM77 simply stops issuing inter- rupts. The 2nd event is another identical rise in temperature. The 3rd event is typical of a drop in temperature. This is one of the conditions that demonstrates the power of the LM77, as the user receives notification that a lower limit is exceeded in such a way that temperature is dropping. The Critical Alarm Event activates the separate T_CRIT_A output. Typically, this would feed circuitry separate from the processor on the assumption that if the system reached this temperature, the processor might not be responding. LM77 www.national.com13
3.0 Application Hints(Continued)
4.0 Typical Applications
Note:Event Interrupt mode is drawn as if the user is reading the part. If the user doesn’t read, the outputs would go low and stay that way until the LM77 is read. FIGURE 7. Temperature Response Diagram for ACPI Implementation FIGURE 8. Typical Application
4.0 Typical Applications(Continued)
FIGURE 9. Remote HVAC temperature sensor communicates via 3 wires, including thermostat signals. FIGURE 10. ACPI Compatible Terminal Alarm Shutdown. By powering the LM77 from auxilary output of the power
Physical Dimensionsinches (millimeters) unless otherwise noted 8-Lead (0.150" Wide) Molded Small Outline Package (SOP), JEDEC Registration Number MS-012 (variation AA), Order Number LM77CIM-3, LM77CIMX-3, LM77CIM-5 or LM77CIMX-5 LM77 www.national.com 16
Physical Dimensionsinches (millimeters) unless otherwise noted (Continued) LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. National Semiconductor Corporation Americas Email: support@nsc.com National Semiconductor Europe Fax: +49 (0) 180-530 85 86 Email: europe.support@nsc.com Deutsch Tel: +49 (0) 69 9508 6208 English Tel: +44 (0) 870 24 0 2171 Français Tel: +33 (0) 1 41 91 8790 National Semiconductor Asia Pacific Customer Response Group Tel: 65-2544466 Fax: 65-2504466 Email: ap.support@nsc.com National Semiconductor Japan Ltd. Tel: 81-3-5639-7560 Fax: 81-3-5639-7507 www.national.com 8-Lead (0.150" Wide) Molded Mini Small Outline Package (MSOP), JEDEC Registration Number MO-187 (variation AA), Order Number LM77CIMM-3, LM77CIMMX-3, LM77CIMM-5 or LM77CIMMX-5 LM77 9-Bit + Sign Digital Temperature Sensor and Thermal Window Comparator with Two-Wire Interface National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.