MIC502_06 Datasheet, PDF (1/15 Pages) Micrel Semiconductor – Fan Management IC

MIC502
Fan Management IC
General Description
Features
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 (option-
ally) 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. Low-
frequency 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 user-
determined 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.
• 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
___________________________________________________________________________________________________________
Typical Application
12V
T1 R1
R3 R2
R4
C_F
Secondary
Fan-contro l
Input
MIC502
1 _{VT1 VDD} 8
2 _CF
OUT ⁷
3 _{VSLP OTF} 6
4 _{GND VT2} 5
Fan
R_BASE
Q1
Overtemperature
Fault Output
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel [phone] • fax + 1 [phone] • http://www.micrel.com
November 2006
1
M9999-112206