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.

Description (continued) 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.

• 8-bit ΣΔ ADC
• Monitors 16 Power Supplies
• Monitors 4 Remote Thermal Diodes and 2 LM60
• NewTruTherm Technology Support for Precision Thermal Diode Measurements
• Internal Ambient Temperature Sensing
• Programmable Autonomous Fan Control Based on Temperature Readings with Fan Boost Support
• Fan Boost Support on Tachometer Limit Error Event
• Fan Control Based on 13-step Lookup Table or PI Control Loop or Combination of Both
• PI Fan Control Loop Supports Tcontrol
• Temperature Reading Digital Filters
• 0.5°C digital Temperature Sensor Resolution
• 0.0625°C Filtered Temperature Resolution for Fan Control
• 2 PWM Fan Speed Control Outputs
• 4 Fan Tachometer Inputs
• Dual Processor Thermal Throttling (PROCHOT) Monitoring
• Dual Dynamic VID Monitoring (6/7 VIDs per processor) Supports VRD10.2/11
• 8 General Purpose I/Os:
  • 4 Can be Configured as Fan tachometer Inputs
  • 2 Can be Configured to Connect to Processor THERMTRIP
  • 2 are Standard GPIOs that Could be Used to Monitor IERR Signal
• 2 General Purpose Inputs that Can be Used to Monitor the 7th VID Signal for VRD11
• Limit Register Comparisons of all Monitored Values
• 2-wire Serial Digital Interface, SMBus 2.0 Compliant
  • Supports Byte/block Read and Write
  • Selectable Slave Address (Tri-level Pin Selects 1 of 3 Possible Addresses)
  • ALERT Output Supports Interrupt or Comparator Modes
• 2.5V Reference Voltage Output
• 56-pin TSSOP Package
• XOR-tree Test Mode

Key Specifications

• Voltage Measurement Accuracy ... ±2% FS (max)
• Temperature Resolution ... 9-bits, 0.5°C
• Temperature Sensor Accuracy ... ±2.5 °C (max)
• Temperature Range:
  • LM94 Operational ... 0°C to +85°C
  • Remote Temp Accuracy ... 0°C to +125°C
• Power Supply Voltage ... +3.0V to +3.6V
• Power Supply Current ... 1.6 mA