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Thermal Management Solutions Dave Hanrahan Applications Engineer

Thermal Management Solutions Dave Hanrahan Applications Engineer. Agenda. A look at the Thermal Problem Thermal Diode Monitoring (TDM) Techniques Thermals vs. Acoustics - associated tradeoffs Distributed Temperature Sensing Automatic Fan Speed Control Demo Wrap-up. The Thermal Problem.

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Thermal Management Solutions Dave Hanrahan Applications Engineer

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  1. Thermal Management Solutions Dave Hanrahan Applications Engineer

  2. Agenda • A look at the Thermal Problem • Thermal Diode Monitoring (TDM) Techniques • Thermals vs. Acoustics - associated tradeoffs • Distributed Temperature Sensing • Automatic Fan Speed Control • Demo • Wrap-up RF Symposium

  3. The Thermal Problem • Equipment required to operate in harsh environments • High Reliability: - demand for 24-7 operation • System down-time can cost $$$$ • Need to reduce TCO (Total Cost of Ownership) • Trend is towards increased component power and component density on cards/modules • Need for predictive failure: - allows equipment to report potential problems before they actually occur RF Symposium

  4. The Thermal Problem: - sources of heat Common to have 100W - 200W to be dissipated RF Symposium

  5. The Thermal Problem:- Design Constraints • Multiple boards in cabinets restrict airflow: - require many fans to deliver adequate volumetric cooling • Low profile systems constrain the amount and physical size of cooling fans limiting CFM delivery • Multiple fans will heavily contribute to system noise and current consumption RF Symposium

  6. Thermal Diode Monitoring (TDM) • A base-emitter PN junction has an inherent temperature dependency which is described by the following equation: - VBE = kT/q * ln (Ic/Is) • PN junction voltage changes by -2mV/°C • Need to extract this low level signal • Remove diode offset • Filter Noise RF Symposium

  7. TDM Sampling Input Stage D- is biased a diode drop above GND I = 12mA, N = 17 Input Low pass filter 65kHz C1 is optional for noisy environments Results averaged over 16 conversions RF Symposium

  8. Temperature from VBE • VBE = kT/q * ln (Ic/Is) • VBE1-VBE2 = DVBE =(kT/q) (ln (I/NI) • Since I,N, k, q are all known constants then • DVBE = (Constant) (T) • or T = (Constant) (DVBE) • Simple transistor can be used to measure temperature • 2-wires can connect to transistor several feet away RF Symposium

  9. Temperature Sensing: 1C Accuracy +3.3V 2N3904 SMBus Alert Over-temperature turns on fan full-speed RF Symposium

  10. Thermals vs. Acoustics • Active cooling makes use of fans to push air • No. fans required depend on: - • system thermal profile • physical size of system • The greater the no. fans, the better the cooling, but to the detriment of acoustics • Automatic Fan Speed Control reduces acoustic noise by optimizing fan speed for measured temperature • Reduces system current consumption RF Symposium

  11. Why implement Fan Speed Control? • Reduce Acoustic Noise • Reduce Current Consumption • Increase Fan Life RF Symposium

  12. Thermals vs. Acoustics • Are there Acoustic Noise Standards to be adhered to? • ISO 7779: - Noise Emitted by Computer & Business Equipment • BLUE ANGEL specs • http://www.nemko.no/s_environmental/engel.html • Acoustic Noise Emitted by Telecommunications Equipment • http://www.etsi.org/ (ETS 300 753) RF Symposium

  13. ISO7779 Measurement Method Bystander 30° Operator • Operator Position - 1.2m from floor, 0.25m from equipment • Bystander Position - 1.5m from floor, 1m from equipment 30° 0.25m 1m 1.5m 1.2m RF Symposium

  14. Acoustic Standards - Blue Angel • Blue Angel specs propose that a PC be no louder than 48dBA in idle state, i.e. with no hard disk or other drive activity. • In the active state, i.e. when the hard disk or another drive is being accessed, the machine should be no noisier than 55dBA. RF Symposium

  15. Acoustic Standards - Telecommunications Equipment (ETSI) * Measurements taken in accordance with ISO7779 RF Symposium

  16. Any shortcomings/concerns? • Specs merely define max “static” noise or noise averaged from equipment over a time period e.g. 24 seconds. • However, a fan may be running quieter than noise limit, but may still be cycling up and down, annoying the user. • Require some method to account for “dynamic noise behaviour” or rate of change of noise. • Filtered Automatic Fan Speed Control Mode is a mechanism with which to defeat this problem. RF Symposium

  17. Fan Noise vs. Temperature Fan Speed Control reduces noise Auto Fan Speed Control RF Symposium

  18. Distributed Temperature Sensing • All Temperature Monitoring devices are intelligent, 2-wire bus-based • Multiple address selection allows up to 9 devices to be placed on a single bus • Multiple remote temperature measurement capability • Low cost and extremely small package options RF Symposium

  19. Distributed Temperature Sensing RF Symposium

  20. Automatic Fan Speed Control • A single temperature or all temperatures can control the fan speed. • Fan Speed varies automatically with temperature. • Only 2 parameters required: TMIN & TRANGE RF Symposium

  21. Automatic Fan Speed Control TRANGE RF Symposium

  22. Effect Of TRANGE Value 13.33% / °C 0.833% / °C RF Symposium

  23. Filtered Auto Fan Speed Control Mode • Allows fan to ramp up or down smoothly to new speed • Less acoustic pollution since fan is not cycling up and down with fast temperature transients RF Symposium

  24. ADM1026 Systems Monitor ASIC • Up to 17 Voltage Measurement Channels for PSUs • Up to 8 Fan Speed Measurement Inputs • Up to 17 GPIOs • Remote Temperature Measurement (2 channels) • On-chip Temperature Sensor • Linear & PWM Fan Speed Control o/p’s • 8kB on-chip EEPROM • Chassis Intrusion Detection • Reset Input, Reset Outputs • Automatic Fan Speed Control RF Symposium

  25. RF Symposium

  26. ADM1026 • Complete systems monitoring solution • Monitors system temperatures, voltages and fan speeds • EEPROM holds FRU information RF Symposium

  27. ADM1026 Software Demo Evaluation software available for all products RF Symposium

  28. ADM1029 Scaleable, Intelligent Fan Controller • Programmable & Automatic Fan Speed Control • Dual Fan Speed Measurement • Supports Backup & Redundant Fans • Supports Hot Swapping of Fans • Cascadable Fault Output (CFAULT) for multiple device communication • Local & Remote Temperature Monitoring • Small 24-pin QSOP package RF Symposium

  29. ADM1029 Scaleable, Intelligent Fan Controller • Fan Free-Wheel Test • All Faults, Alarms Are fully Maskable • Up to 8 Devices may be addressed in a system using a single address pin (controlling up to 16 Fans) • Normal, Alarm & HotPlug speeds are all programmable • OFFSET Registers allow offset values to be added to default temperature measurements • 15.625Hz, 62.5Hz, 250Hz, & 1kHz PWM drive frequencies available RF Symposium

  30. ADM1029 Application Circuit RF Symposium

  31. ADM1030/ADM1031 Intelligent Temperature Monitor/Fan Controllers • Programmable & Automatic Fan Speed Control • RPM Mode to maintain constant fan speed • Remote Temperature Measurement accurate to 1C • 0.125°C Resolution on Remote Temperature channel • Local Temp Sensor with 0.25°C Resolution • Pulse Width Modulation (PWM) Fan Control • Programmable PWM Frequency (10Hz to 100Hz) • Tach Fan Speed Measurement for 3-wire fans • Analog input measures speed of 2-wire fans RF Symposium

  32. ADM1030/ADM1031 Features • Programmable PWM duty cycle (0% to 100%) • Over Temperature (THERM) output • Filtered Mode helps dynamic acoustic variations by filtering fans response to temperature transients • FAN_FAULT output signals catastrophic fan failure to system RF Symposium

  33. ADM1030 Application Circuit N.C. pins represent 2nd temp. & fan channel on ADM1031 RF Symposium

  34. For more information: • www.analog.com/pc • www.analog.com/temp-sensors • email: david.hanrahan@analog.com RF Symposium

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