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Thermal Management Solutions Dave Hanrahan Applications Engineer

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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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Presentation Transcript
slide1

Thermal Management Solutions

Dave Hanrahan

Applications Engineer

agenda
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

the thermal problem
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

the thermal problem sources of heat
The Thermal Problem: - sources of heat

Common to have 100W - 200W to be dissipated

RF Symposium

the thermal problem design constraints
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

thermal diode monitoring tdm
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

tdm sampling input stage
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

temperature from v be
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

temperature sensing 1 c accuracy
Temperature Sensing: 1C Accuracy

+3.3V

2N3904

SMBus

Alert

Over-temperature

turns on fan

full-speed

RF Symposium

thermals vs acoustics
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

why implement fan speed control
Why implement Fan Speed Control?
  • Reduce Acoustic Noise
  • Reduce Current Consumption
  • Increase Fan Life

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thermals vs acoustics12
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)

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iso7779 measurement method
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

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acoustic standards blue angel
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.

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acoustic standards telecommunications equipment etsi
Acoustic Standards - Telecommunications Equipment (ETSI)

* Measurements taken in accordance with ISO7779

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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

distributed temperature sensing
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

automatic fan speed control
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

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automatic fan speed control21
Automatic Fan Speed Control

TRANGE

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slide22

Effect Of TRANGE Value

13.33% / °C

0.833% / °C

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slide23

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

slide24

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

adm1026
ADM1026
  • Complete systems monitoring solution
  • Monitors system temperatures, voltages and fan speeds
  • EEPROM holds FRU information

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adm1026 software demo
ADM1026 Software Demo

Evaluation software available for all products

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slide28

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

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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

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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

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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

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slide33

ADM1030 Application Circuit

N.C. pins represent 2nd temp. & fan channel on ADM1031

RF Symposium

for more information
For more information:

RF Symposium

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