MIC5020

Micrel

October 1998

5-163

5

Pin Description

Pin Number

Pin Name

Pin Function

1V

DD

Supply: +11V to +50V. Decouple with

≥ 10µF capacitor.

2

Input

TTL Compatible Input: Logic high turns the external MOSFET on. An internal

pull-down returns an open pin to logic low.

3

Fault

Overcurrent Fault Indicator: When the sense voltage exceeds threshold,

open collector output is open circuit for 5

µs (t

t

4C

T

Retry Timing Capacitor: Controls the off time (t

retry cycle. (Duty cycle adjustment.)

• Open = 20% duty cycle.

• Capacitor to Ground = approx. 20% to <1% duty cycle.

• Pull-Up resistor = approx. 20% to approx. 75% duty cycle.

• Ground = maintained shutdown upon overcurrent condition.

5

Gnd

Circuit Ground

6

Sense +

Current Sense Comparator (+) Input: Connect to high side of sense resistor

or current sensing MOSFET sense lead. A built-in offset in conjunction with

R

7

Sense –

Current Sense Comparator (–) Input: Connect to the low side of the sense

resistor (usually power ground).

8

Gate

Gate Drive: Drives the gate of an external power MOSFET. Also limits V

GS

to 15V max. to prevent Gate to Source damage. Will sink and source

current.

Pin Configuration

1

2

3

4

8

7

6

5

Input

Fault

Gate

Sense

−

Sense

+

Gnd

1

2

3

4

8

7

6

5

Gate

Sense

−

Sense

+

Gnd

Input

Fault

Block Diagram

Sense –

Sense +

6V Internal Regulator

50mV

Input

ONE-

SHOT

Gate

Fault

6V

OFF

ON

Fault

Normal

Q1

↓

↑

Transistor Count: 82

DIP Package

SOIC Package

(N)

(M)