LM78 Microprocessor System Hardware Monitor | TI.com

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Microprocessor System Hardware Monitor

Microprocessor System Hardware Monitor - LM78

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The LM78 is a highly integrated Data Acquisition system for hardware monitoring of servers, Personal Computers, or virtually any microprocessor based system. In a PC, the LM78 can be used to monitor power supply voltages, temperatures, and fan speeds. Actual values for these inputs can be read at any time, and programmable WATCHDOG limits in the LM78 activate a fully programmable and maskable interrupt system with two outputs.

The LM78 has an on-chip temperature sensor, 5 positive analog inputs, two inverting inputs (for monitoring negative voltages), and an 8-bit ADC. An input is provided for the overtemperature outputs of additional temperature sensors and this is linked to the interrupt system. The LM78 provides inputs for three fan tachometer outputs. Additional inputs are provided for Chassis Intrusion detection circuits, VID monitor inputs, and chainable interrupt. The LM78 provides both ISA and Serial Bus interfaces. A 32-byte auto-increment RAM is provided for POST (Power On Self Test) code storage.


  • Temperature sensing
  • 5 positive voltage inputs
  • 2 op amps for negative voltage monitoring
  • 3 fan speed monitoring inputs
  • Input for additional temperature sensors
  • Chassis Intrusion Detector input
  • WATCHDOG comparison of all monitored values
  • POST code storage RAM
  • ISA and I2C™ Serial Bus interfaces

Key Specifications

Voltage monitoring accuracy ±1% (max)
Temperature Accuracy -10°C to +100°C ±3°C (max)
Supply Voltage 5V
Supply CurrentOperating:1 mA typ
 Shutdown:10 µA typ
ADC Resolution 8 Bits

I2C® is a registered trademark of the Phillips Corporation.