MIC502 Fan Management IC0 pages

MIC502
Fan Management IC
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
November 2006 1 M9999-112206
General Description
The MIC502 is a thermal and fan management IC which
supports the features for NLX/ATX power supplies and
other control applications.
Fan speed is determined by an external temperature
sensor, typically a thermistor-resistor divider, and (optionally)
a second signal, such as the NLX “FanC” signal. The
MIC502 produces a low-frequency pulse-width modulated
output for driving an external motor drive transistor. Lowfrequency
PWM speed control allows operation of
standard brushless dc fans at low duty cycle for reduced
acoustic noise and permits the use of a very small power
transistor. The PWM time base is determined by an
external capacitor.
An open-collector overtemperature fault output is asserted
if the primary control input is driven above the normal
control range.
The MIC502 features a low-power sleep mode with a userdetermined
threshold. Sleep mode completely turns off the
fan and occurs when the system is asleep or off (both
control inputs very low). A complete shutdown or reset can
also be initiated by external circuitry as desired.
The MIC502 is available as 8-pin plastic DIP and SOIC
packages in the –40°C to +85°C industrial temperature
range.
Data sheets and support documentation can be found on
Micrel’s web site at www.micrel.com.
Features
• Temperature-proportional fan speed control
• Low-cost, efficient PWM fan drive
• 4.5V to 13.2V IC supply range
• Controls any voltage fan
• Overtemperature detection with fault output
• Integrated fan startup timer
• Automatic user-specified sleep mode
• Supports low-cost NTC/PTC thermistors
• 8-pin DIP and SOIC packages
Applications
• NLX and ATX power supplies
• Personal computers
• File servers
• Telecom and networking hardware
• Printers, copiers, and office equipment
• Instrumentation
• Uninterruptible power supplies
• Power amplifiers
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Typical Application
VT1
CF
VSLP
GND
VDD
OUT
OTF
VT2
1
2
3
4
8
7
6
5
T1 R1
R3
R4
CF
R2
12V
RBASE
Overtemperature
Fault Output
MIC502
Secondary
Fan-contro l
Input
Fan
Q1