6

HV57009

Typical Current Programing Circuits

+IN

-IN

HV57009

Logic

To other

outputs

- +

0.1µF

VREF

IOUT

HVOUT

VDD

0.1µF

VBP

IREF

REXT

+IN

-IN

HV57009

Logic

To other

outputs

-+

VSS

Figure 1b: Positive Control

Figure 1a: Negative Control

VREF

IOUT

HVOUT

VDD

VBP

IREF

REXT

VSS

*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

‌ V

R

EXT

HV570 I

OUT

vs. V

REF

0

1

2

3

4

012

345

0.5K

0.1K

0.2K

1K

2K

3K

5K

V

REF

I

REF

V

REF

I

OUT