HCPL788J datasheet(13/20 Pages) HP

13 / 20 page

Analog Interfacing

Power Supplies and Bypassing

The recommended supply con-

nections are shown in Figure 26.

A floating power supply (which in

many applications could be the

same supply that is used to drive

the high-side power transistor) is

regulated to 5 V using a simple

zener diode (D1); the value of

resistor R4 should be chosen to

supply sufficient current from

Figure 25. Recommended Applications Circuit.

Figure 26. Recommended Supply and Sense Resistor Connections.

the existing floating supply. The

voltage from the current sensing

resistor (Rsense) is applied to the

input of the HCPL-788J through

an RC anti-aliasing filter (R2 and

C2). Although the application

circuit is relatively simple, a

few recommendations should

be followed to ensure optimal

performance.

The power supply for the

HCPL-788J is most often obtained

from the same supply used to

power the power transistor gate

drive circuit. If a dedicated

supply is required, in many cases

it is possible to add an additional

winding on an existing trans-

former. Otherwise, some sort of

simple isolated supply can be

used, such as a line powered

GND2

VDD2

FAULT

ABSVAL

VOUT

VREF

VDD2

GND2

VIN+

VIN-

VDD1

VLED1+

VDD1

GND1

RSHUNT

0.02

Ω

ISOLATED +5 V

R3 4.7 k

Ω

.01 µF

0.1 µF

HCPL-788J

INPUT

CURRENT

+5 V

A/D

VREF

GND

µC

TO OTHER

PHASE OUTPUTS

0.1 µF

C5 = C7 = C8 = 470 pF

C4 = 0.1 µF

GND2

VDD2

FAULT

ABSVAL

VOUT

VREF

VDD2

GND2

VDD1

VIN+

VIN-

GND1

VDD1

VLED+

Ω

0.1 µF

0.01 µF

FLOATING

POWER

SUPPLY

HV+

–

RSENSE

HV-

MOTOR

5.1 V

GATE DRIVE

CIRCUIT

HCPL-788J

HCPL788J Datasheet(PDF) 13 Page - Agilent(Hewlett-Packard)

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