OPA547

11

SBOS056F

www.ti.com

Output Disable and Thermal Shutdown Status

As mentioned earlier, the OPA547’s output can be disabled

and the disable status can be monitored simultaneously.

Figures 9 and 10 provide examples using a single supply and

dual supplies, respectively.

OPA547

V+

E/S

Open Drain

(Output Disable)

HCT

(Thermal Status

Shutdown)

V–

FIGURE 9. Output Disable and Thermal Shutdown Status with

a Single Supply.

OUTPUT PROTECTION

Reactive and EMF-generating loads can return load cur-

rent to the amplifier, causing the output voltage to exceed

the power-supply voltage. This damaging condition can be

avoided with clamp diodes from the output terminal to the

power supplies, as shown in Figure 11. Schottkey rectifier

diodes with a 1A or greater continuous rating are recom-

mended.

FIGURE 10. Output Disable and Thermal Shutdown Status with Dual Supplies.

FIGURE 11. Motor Drive Circuit.

G = –

= –4

R

2

R

1

3

Ω

(Carbon)

0.01

µF

R

2

20k

Ω

R

1

5k

Ω

OPA547

V–

V+

V

IN

Motor

D

1

D

2

D

OPA547

V+

E/S

NOTE: (1) Optional—may be required to limit leakage

current of optocoupler at high temperatures.

V–

(1)

6

1

2

4N38

Optocoupler

5

4

HCT or TTL In

5V

6

2

1

4N38

Optocoupler

5

4

Zetex

ZVN3310

TTL Out

7.5k

Ω

1W

5V

OUTPUT STAGE COMPENSATION

The complex load impedances common in power op amp

applications can cause output stage instability. For normal

operation output compensation circuitry is not typically re-

quired. However, if the OPA547 is intended to be driven into

current limit, a R/C network may be required. Figure 11

shows an output series R/C compensation (snubber) net-

work (3

Ω in series with 0.01µF) which generally provides

excellent stability. Some variations in circuit values may be

required with certain loads.