4

Rev. 1.0

06/06/03

IRU3039

www.irf.com

Figure 2 - Simplified block diagram of the IRU3039.

BLOCK DIAGRAM

PIN DESCRIPTIONS

Output of internal regulator. The output is protected for short circuit. A high frequency

capacitor is recommended to be connected from this pin to ground.

This pin is connected to the Drain of the lower MOSFET via an external resister and it

provides the positive sensing for the internal current sensing circuitry. The external resis-

An external capacitor can be placed in parallel with the programming resistor to provide

high frequency noise filtering.

This pin provides soft-start for the switching regulator. An internal current source charges

an external capacitor that is connected from this pin to ground which ramps up the output

of the switching regulator, preventing it from overshooting as well as limiting the input

current. The converter can be shutdown by pulling this pin down below 0.4V.

Compensation pin of the error amplifier. An external resistor and capacitor network is

typically connected from this pin to ground to provide loop compensation.

This pin is connected directly to the output of the switching regulator via resistor divider to

provide feedback to the Error amplifier.

Non-inverting input of error amplifier.

No connection.

PIN#

PIN SYMBOL

PIN DESCRIPTION

15

16

17

18

19

20

2,3,5,

11,13,14

OCSet

SS / SD

Comp

Fb

NC

22uA

64uA Max

POR

Oscillator

Error Amp

Ct

Error Comp

Reset Dom

POR

0.4V

FbLo Comp

Vc

HDrv

Vcc

LDrv

PGnd

Vcc

4V

Vc

3.5V

0.2V

0.2V

Bias

Generator

3V

1.25V

POR

SS / SD

Fb

Comp

25K

25K

3V

R

S

Q

Rt

Gnd

Rt

17

19

18

12

10

9

6

7

8

OC Comp

OCSet

3V

28uA

Regulator

6V

16

15

1.25V

1

Enbl

4

0.8V