6

Supertex inc.

www.supertex.com

Doc.# DSFP-HV57009

A061913

HV57009

Typical Current Programing Circuits

+IN

-IN

R

HV57009

Logic

To other

outputs

- +

VREF

I

OUT

HVOUT

VDD

0.1µF

VBP

I

REF

R

EXT

+IN

-IN

C

HV57009

Logic

To other

outputs

-+

VSS

Figure 1b: Positive Control

Figure 1a: Negative Control

VREF

I

OUT

HVOUT

VDD

VBP

I

REF

R

EXT

VSS

0.1µF

R

C

*Required if R

Since:

I

Therefore:

If I

If I

If R

stability as shown.

This control method behaves linearly as long as the opera-

tional amplifier is not saturated. However, it requires a nega-

tive power source and needs to provide a current I

for each HV570 chip being controlled.

If HV

ate as a perfect current source, and the output current will

diminish. This effect depends on the magnitude of the output

current.

Given I

R

The intersection of a set of I

cated in the graph shown below. The value picked for R

EXT

must always be in the shaded area for linear operation. This

control method has the advantage that V

draws only leakage current. If R

work R

Note:

Lower reference current I

∆I

HV57009 I

4

3

2

1

0

0

1

2

3

4

5

V

0.1k

0.2k

0.5k

1.0k

2.0k 3.0k

5.0K