MIC502

Fan Management IC

Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (

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 (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.

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

___________________________________________________________________________________________________________

Typical Application

VT1

CF

VS L P

GND

VDD

OUT

OT F

VT2

1

2

3

4

8

7

6

5

R1

T1

R3

R4

R2

12V

Overtemperature

Fault Output

MIC502

Secondary

Fan-contro

l

Input

Fan

Q1