7

HV9120/HV9123

1

8

4

5

6

7

16

9

15

14

13

12

11

10

1

8

2

3

4

5

6

7

16

9

15

14

13

12

11

10

BIAS

FB

COMP

Reset

Shutdown

V

REF

Discharge

OSC In

Error Amplifier

The error amplifier in the HV912x is a true low-power differential

input operational amplifier intended for around-the-amplifier com-

pensation. It is of mixed CMOS-bipolar construction: A PMOS

input stage is used so the common-mode range includes ground

and the input impedance is very high. This is followed by bipolar

gain stages which provide high gain without the electrical noise of

all-MOS amplifiers. The amplifier is unity-gain stable.

Current Sense Comparators

The HV912x uses a true dual comparator system with indepen-

dent comparators for modulation and current limiting. This allows

the designer greater latitude in compensation design, as there are

no clamps (except ESD protection) on the compensation pin. Like

the error amplifier, the comparators are of low-noise BiCMOS

construction.

Remote Shutdown

The shutdown and reset pins of the HV912x can be used to

perform either latching or non-latching shutdown of a converter as

required. These pins have internal current source pull-ups so they

can be driven from open-drain logic. When not used they should

be left open, or connected to V

Output Buffer

The output buffer of the HV912x is of standard CMOS construc-

tion (P-channel pull-up, N-channel pull-down). Thus the body-

drain diodes of the output stage can be used for spike clipping if

necessary, and external Schottky diode clamping of the output is

not required.

+V

IN

NC

NC

Sense

Output

–V

IN

V

DD

OSC Out

Pinout

16 Pin SOIC

top view

Note: Pins 2 and 3 are removed

16 Pin Dip Package

top view

BIAS

FB

COMP

Reset

Shutdown

Discharge

OSC In

+V

IN

Sense

Output

–V

IN

V

DD

OSC Out

19

20

1

2

3

18

17

16

15

14

13

12

11

10

9

4

5

6

7

8

•

FB

BIAS

NC

NC

+V

IN

NC

Discharge

OSC In

OSC Out

V

DD

20-pin PJ Package

top view

1235 Bordeaux Drive, Sunnyvale, CA 94089

TEL: (408) 744-0100 • FAX: (408) 222-4895

www.supertex.com

11/12/01

©2001 Supertex Inc. All rights reserved. Unauthorized use or reproduction prohibited.