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HV57009PG-G

64-Channel Serial to Parallel Converter with P-Channel Open Drain Controllable Output Current

Supertex Inc 

Typical Current Programing Circuits

0.1µF

VDD

HV57009

0.1µF

VDD

HV57009

HV57009

VBP

-+

Logic

To other

outputs

IOUT

VBP

-+

Logic

To other

outputs

+IN -IN

HVOUT

+IN -IN

REXT

IREF

VREF

RD *10kΩ

CD *390pF

VSS

VREF

REXT

IREF

RD *10kΩ

CD *390pF

VSS

Figure 1a: Negative Control

Figure 1b: Positive Control

*Required if REXT > 10KΩ or REXT is replaced by a constant current source.

IOUT

HVOUT

Since:

IOUT = IREF = │ VREF │ / REXT

Therefore:

If IOUT = 2.0mA and VREF = -5.0V → REXT = 2.5KΩ.

If IOUT = 1.0mA and REXT = 1.0KΩ → VREF = -1.0V.

If REXT >10KΩ, add series network RD and CD to ground for

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 IREF = IOUT

for each HV570 chip being controlled.

If HVOUT ≥ +1.0V, the HVOUT cascade may no longer oper-

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

diminish. This effect depends on the magnitude of the output

current.

Given IOUT and VREF, the REXT can be calculated by using:

REXT = VREF / IREF = VREF / IOUT

The intersection of a set of IOUT and VREF values can be lo-

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

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

control method has the advantage that VREF is positive, and

draws only leakage current. If REXT > 10KΩ, add series net-

work RD and CD to ground for stability as shown.

Note:

Lower reference current IREF, results in higher distortion,

∆ICS, on the output.

HV57009 IOUT vs. VREF

4

0.1k

0.2k

0.5k

1.0k

2.0k 3.0k

3

2

5.0K

1

Doc.# DSFP-HV57009

A061913

00

1

2

3

4

5

VREF (V)

Supertex inc.

6

www.supertex.com

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