Part # LM87 datasheet

Part Manufacturer: National Semiconductor

National Semiconductor

Part Description: LM87 Serial Interface System Hardware Monitor with Remote Diode Temperature Sensing


Part Details:

LM87 December 2003 Serial LM87Serial Interface System Hardware Monitor with Remote Interface Diode Temperature SensingGeneral Description n 2 inputs selectable for fan speed or voltage monitoring n 8-bit DAC output for controlling fan speed The LM87 is a highly integrated data acquisition system for n Chassis Intrusion Detector input System hardware monitoring of servers, Personal Computers, orvirtually any microprocessor-based system. In a PC, the n WATCHDOG comparison of all monitored values LM87 can be used to monitor power supply voltages, moth- n SMBus or I2C Serial Bus interface compatibility erboard and processor temperatures, and fan speeds. Ac- n VID0-VID4 or IRQ0-IRQ4 monitoring inputs tual values for these inputs can be read at any time. Pro- n On chip temperature sensor grammable WATCHDOG limits in the LM87 activate a fully Hardware programmable and maskable interrupt system with two out- Key Specifications puts (INT# and THERM#). The LM87 has an on-chip digital output temperature sensor j Voltage Monitoring Error ±2 % (max) with 8-bit resolution as well as the capability of monitoring 2 j External Temperature Error ±4 °C (max) external diode temperatures to 8-bit resolution, an 8 channel j Internal Temperature Error analog input ADC with 8-bit resolution and an 8-bit DAC. A -40 °C to +125 °C ± 3 °C (typ) channel on the ADC measures the supply voltage applied to Monitor the LM87, nominally 3.3 V. Two of the ADC inputs can be j Supply Voltage Range 2.8 to 3.8 V redirected to a counter that can measure the speed of up to j Supply Current 0.7 mA (typ) 2 fans. A slow speed ADC architecture allows stable j ADC and DAC Resolution 8 Bits measurement of signals in an extremely noisy environment.The DAC, with a 0 to 2.5 V output voltage range, can be j Temperature Resolution 1.0 °C used for fan speed control. Additional inputs are provided for with Chassis Intrusion detection circuits, and VID monitor inputs. Applications The VID monitor inputs can also be used as IRQ inputs if VIDmonitoring is not required. The LM87 has a Serial Bus n System Thermal and Hardware Monitoring for Servers,


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LM87.pdf Datasheet