Overview
The LM77CIMM-3/NOPB is a digital temperature sensor and thermal window comparator produced by Texas Instruments. It features an I2C Serial Bus interface, making it highly versatile for various thermal management and protection applications. The device is designed to simplify the design of temperature control systems, particularly those conforming to the ACPI (Advanced Configuration and Power Interface) specification for personal computers. It includes separate open-drain outputs for interrupt and critical temperature shutdown, and it can operate in shutdown mode to minimize power consumption.
Key Specifications
| Specification | Value |
|---|---|
| Supply Voltage | 3.0V to 5.5V |
| Supply Current | Operating: 250 μA (typ), 500 μA (max) Shutdown: 5 μA (typ) |
| Temperature Accuracy | −10°C to 65°C: ±1.5°C (max) −25°C to 100°C: ±2°C (max) −55°C to 125°C: ±3°C (max) |
| Operating Temperature Range | −55°C to 125°C |
| Package | SOIC (D) 8-pin, VSSOP 8-pin |
Key Features
- Window-comparator architecture simplifies design of ACPI compatible temperature monitoring and control.
- I2C Serial Bus interface.
- Separate open-drain outputs for interrupt and critical temperature shutdown.
- Shutdown mode to minimize power consumption.
- Up to 4 LM77s can be connected to a single bus.
- 9-bit + sign output; full-scale reading of over 128°C.
- Programmable hysterisis and fault queue to minimize false tripping.
- Address selection via two pins (A0, A1).
Applications
The LM77 is ideal for a wide range of applications, including thermal management and protection in personal computers, electronic test equipment, office electronics, automotive systems, and HVAC applications.
Q & A
- What is the supply voltage range of the LM77?
The supply voltage range is 3.0V to 5.5V. - What is the typical operating current of the LM77?
The typical operating current is 250 μA. - What is the temperature accuracy of the LM77 in the range of −10°C to 65°C?
The temperature accuracy is ±1.5°C (max). - Can multiple LM77 devices be connected to a single bus?
Yes, up to 4 LM77s can be connected to a single bus. - What is the purpose of the INT and T_CRIT_A outputs?
The INT output becomes active when the temperature goes outside a programmable window, and the T_CRIT_A output becomes active when the temperature exceeds a programmable critical limit. - How does the LM77 minimize power consumption?
The LM77 has a shutdown mode to minimize power consumption. - What is the resolution of the temperature data output by the LM77?
The temperature data is represented by a 10-bit, two's complement word with an LSB equal to 0.5°C. - What are the default thresholds for the LM77 when it powers up?
The default thresholds are 2°C T_HYST, 10°C T_LOW, 64°C T_HIGH, and 80°C T_CRIT. - Can the LM77 be used in automotive applications?
Yes, the LM77 is suitable for use in automotive applications. - What is the operating temperature range of the LM77?
The operating temperature range is −55°C to 125°C.
