The LM94 hardware monitor has a two wire digital interface compatible with SMBus 2.0.
Using a ΣΔ ADC, the LM94 measures the temperature of four remote diode connected transistors as
well as its own die and 16 power supply voltages. The LM94 has new TruTherm technology that
supports precision thermal diode measurements of processors on sub-micron processes.
To set fan speed, the LM94 has two PWM outputs that are each controlled by up to six
temperature zones. The fan-control algorithm can be based on a lookup table, PI
(proportional/integral) control loop, or a combination of both. The LM94 includes digital filters
that can be invoked to smooth temperature readings for better control of fan speed such that
acoustical noise is minimized. The LM94 has four tachometer inputs to measure fan speed. Limit and
status registers for all measured values are included.
The LM94 builds upon the functionality of previous motherboard server management ASICs,
such as the LM93. It also adds measurement and control support for dynamic Vccp monitoring for
VRD10/11 and PROCHOT. It is designed to monitor a dual processor Xeon class
motherboard with a minimum of external components.
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