Power Management IPS20 and IPS21

© Copyright 2006-2009 - ASIC Advantage, Inc.

AADS00001/AA743

- Revision 5– Dec 2008

2 / 12

FUNCTIONAL BLOCK DIAGRAM

PIN DESCRIPTION

PIN

Description

1- VCC

IC positive supply pin.

The chip behaves like a 4 volt zener diode referenced to GND

2- VS

Voltage sensing pin.

This is the inverting input of the voltage error amplifier. The positive input of the amplifier is connected

to an internal trimmed 1.20V voltage reference. An external voltage divider connected to this point sets

the output voltage. This pin is also used for voltage loop compensation when required.

3- VCOMP

Voltage loop compensation pin.

This is the output of the voltage error amplifier. The voltage loop compensation network, when required,

is connected between this point and VS pin. Please note that this pin is not a zero-impedance node (1K

Ω

nominal).

4- OPTO

Optocoupler driver pin.

This pin drives and external optocoupler connected to GND. A current-mode drive is used for maximum

noise rejection.

5- ICOMP

Current loop compensation pin. (similar to VCOMP)

This is the output of the current error amplifier. The current loop compensation network, when required,

is connected between this point and the IS pin. Please note that this is not a zero-impedance point (1K

Ω

nominal).

6- IS

Current sensing pin.

This pin is the inverting input of the current sense amplifier. The positive input of the amplifier is

connected to an internal trimmed reference. The sensing threshold is 50mV PTAT (IPS20) or 100mV

constant (IPS21). This pin should be connected through a resistor to the external current sensing resistor.

7- OUT (-)

Negative output pin.

This pin is the negative side of the 1.20V trimmed voltage reference. It should be connected to the

negative output of the SMPS.

8- GND

Ground pin.

This is the most negative IC pin. The first output decoupling capacitor should return to it. Do not confuse

this pin with the IS pin and the OUT(-) pin which are described above.

IS

VS

OPTO

VCOMP

Trimmed 1.25V

Temp. Stable

Bandgap Regulator

VCC

VOLTAGE

ERROR

AMPLIFIER

CURRENT

ERROR

AMPLIFIER

GND

ICOMP

OUT (-)

IPS20 / IPS21

1

2

3

4

5

6

7

8

OPTOCOUPLER

CURRENT-SOURCE

CONTROL

4V Shunt Regulator

Trimmed

Current Sensing

50mV PTAT

100mV Temp.Stable