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PDF LM77CIM-5 Data sheet ( Hoja de datos )
| Número de pieza | LM77CIM-5 | |
| Descripción | 9-Bit Sign Digital Temperature Sensor and Thermal Window Comparator with Two-Wire Interface | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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June 1999
LM77
9-Bit + Sign Digital Temperature Sensor and Thermal
Window Comparator with Two-Wire Interface
General Description
The LM77 is a digital temperature sensor and thermal win-
dow comparator with an I2C™ Serial Bus interface. The
window-comparator architecture of the LM77 eases the de-
sign of temperature control systems conforming to the ACPI
(Advanced Configuration and Power Interface) specification
for personal computers. The open-drain Interrupt (INT) out-
put becomes active whenever temperature goes outside a
programmable window, while a separate Critical Tempera-
ture Alarm (T_CRIT_A) output becomes active when the
temperature exceeds a programmable critical limit. The INT
output can operate in either a comparator or event mode,
while the T_CRIT_A output operates in comparator mode
only.
The host can program both the upper and lower limits of the
window as well as the critical temperature limit. Program-
mable hysterisis as well as a fault queue are available to
minimize false tripping. Two pins (A0, A1) are available for
address selection. The sensor powers up with default thresh-
olds of 2˚C THYST, 10˚C TLOW, 64˚C THIGH, and 80˚C
T_CRIT.
The LM77’s 3.0V to 5.5V supply voltage range, Serial Bus in-
terface, 9-bit + sign output, and full-scale range of over
128˚C make it ideal for a wide range of applications. These
include thermal management and protection applications in
personal computers, electronic test equipment, office elec-
tronics, automotive, and HVAC applications.
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
Key Specifications
n Supply Voltage
n Supply Current
n Temperature
Accuracy
operating
shutdown
−10˚C to 65˚C
−25˚C to 100˚C
−55˚C to 125˚C
3.0V to 5.5V
250 µA (typ)
500 µA (max)
5 µA (typ)
±1.5˚C(max)
±2˚C(max)
±3˚C(max)
Applications
n System Thermal Management
n Personal Computers
n Office Electronics
n Electronic Test Equipment
n Automotive
n HVAC
Simplified Block Diagram
I2C® is a registered trademark of Philips Corporation.
© 1999 National Semiconductor Corporation DS100136
DS100136-1
www.national.com
1 page  
Logic Electrical Characteristics (Continued)
SERIAL BUS
Vdc ±10% for
DIGITAL SWITCHING CHARACTERISTICS Unless otherwise noted, these specifications
LM77CIM-5, +VS=+3.3 Vdc ±10% for LM77CIM-3, CL (load capacitance) on output lines
apply for +VS=+5
= 80 pF unless other-
wise specified. Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = +25˚C,
The switching characteristics of the LM77 fully meet or exceed the published specifications of the
unless otherwise noted.
I2C bus. The following pa-
rameters are the timing relationship between SCL and SDA signal related to the LM77. They are not the I2C bus specifica-
tions.
Symbol
Parameter
Conditions
Typical
(Note 8)
Limits
(Note 9)
Units
(Limit)
t1 SCL (Clock) Period
t2 Data in Set-Up Time to SCL High
t3 Data Out Stable after SCL Low
t4 SDA Low Set-Up Time to SCL Low (Start Condition)
t5 SDA High Hold Time after SCL High (Stop Condition)
2.5 µs(min)
100 ns(min)
0 ns(min)
100 ns(min)
100 ns(min)
DS100136-4
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 > +VS) 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 Semicon-
ductor 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.
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 ac-
curacy 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 to Section 1.1, TEMPERATURE COMPARISON, and Figure 3.
Note 14: Default values set at power up.
5 www.national.com
5 Page 
2.0 I2C Timing Diagrams
DS100136-9
Typical 2-Byte Read From Preset Pointer Location Such as Temp or Comparison Registers
DS100136-10
Typical Pointer Set Followed by Immediate Read for 2-Byte Register such as Temp or Comparison Registers
DS100136-11
Typical 1-Byte Read from Configuration Register with Preset Pointer
Typical Pointer Set Followed by Immediate Read from Configuration Register
DS100136-12
Configuration Register Write
Comparison Register Write
FIGURE 6. Timing Diagrams
DS100136-13
DS100136-14
11 www.national.com
11 Page | ||
| Páginas | Total 15 Páginas | |
| PDF Descargar | [ Datasheet LM77CIM-5.PDF ] | |
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