MIC2172/3172

Micrel, Inc.

M9999-042205

2

April 2005

Ordering Information

Part Number

Temperature

Standard

Pb-Free

Range

Package

MIC2172BN

MIC2172YN

–40°C to +85°C

8-pin plastic DIP

MIC2172BM

MIC2172YM

–40°C to +85°C

8-lead SOIC

MIC3172BN

MIC3172YN

–40°C to +85°C

8-pin plastic DIP

MIC3172BM

MIC3172YM

–40°C to +85°C

8-lead SOIC

8-lead SOIC (M)

1

2

3

4

S GND

COMP

P GND 1

FB

P GND 2

8

7

6

5

Pin Configuration

1

2

3

4

S GND

COMP

P GND 1

FB

P GND 2

8

7

6

5

Pin Description

Pin Number

Pin Name

Pin Function

1S GND

Signal Ground: Internal analog circuit ground. Connect directly to the input

filter capacitor for proper operation (see applications info). Keep separate

from power grounds.

2

COMP

Frequency Compensation: Output of transconductance type error amplifier.

Primary function is for loop stabilization. Can also be used for output voltage

soft-start and current limit tailoring.

3FB

Feedback: Inverting input of error amplifier. Connect to external resistive

divider to set power supply output voltage.

4 (MIC2172)

SYNC

Synchronization/Frequency Adjust: Capacitively coupled input signal greater

than device’s free running frequency (up to 135kHz) will lock device’s

oscillator on falling edge. Oscillator frequency can be trimmed up to 135kHz

by adding a resistor to ground. If unused, pin must float (no connection).

4 (MIC3172)

EN

Enable: Apply TTL high or connect to V

TTL low or connect to ground to disable the regulator. Device draws only

leakage current (<1µA) when disabled.

5V

IN

Supply Voltage: 3.0V to 40V

6P GND 2

Power Ground #2: One of two NPN power switch emitters with 0.3Ω current

sense resistor in series. Required. Connect to external inductor or input

voltage ground depending on circuit topology.

7V

SW

Power Switch Collector: Collector of NPN switch. Connect to external

inductor or input voltage depending on circuit topology.

8P GND 1

Power Ground #1: One of two NPN power switch emitters with 0.3Ω current

sense resistor in series. Optional. For maximum power capability connect

to P GND 2. Floating pin reduces current limit by a factor of two.

8-pin DIP (N)