PA162

PA162U

5

P r o d u c t I n n o v a t i o n F r o m

TYPICALAPPLICATION(CONT)

The amplifiers are especially well-suited for applications

such as this. The extended common mode range allows

command inputs as low as 0V. The output swing lets

it drive within 2V of the supply at an output of 1A. This

means that a command input that ranges from 0 to 10V

will drive a 24V motor from full scale CCW to full scale

CW at ±1A.

-Vs (pins 11, 15, 16 and 20) must be tied to the heatslug

externally on the PCB. To ease metal routing on the PCB,

run a direct trace from the -Vs pin to the center heat slug.

The PA162 can be used in a three amplifier configuration

for a three phase inverter or motor as shown in Figure 4.

GENERAL

Please read Application Note 1 "General Operating Con-

siderations" which covers stability, supplies, heatsinking,

mounting, SOA interpretation, and specification interpre-

tation. Visit www.cirrus.com for design tools that help automate tasks such as calculations for stability, internal

power dissipation, heatsink selection; Apex Precision Power's complete Application Notes library; Technical Semi-

nar Workbook; and Evaluation Kits.

STABILITYCONSIDERATIONS

All monolithic power op amps use output stage topologies that present special sta-

bility problems. This is primarily due to non-complementary (both devices are NPN)

output stages with a mismatch in gain and phase response for different polarities of

output current. It is difficult for the op amp manufacturer to optimize compensation

for all operating conditions. For applications with load current exceeding 300mA,

oscillation may appear. The oscillation may occur only with the output voltage swing

at the negative or positive half cycle. Under most operating and load conditions

acceptable stability can be achieved by providing a series RC snubber network

connected from the output to ground (see Figure 5). The recommended component

values of the network are, R

Note 1 for further details.

SAFEOPERATINGAREA(SOA)

The SOA curves combine the effect of all limits for this

power op amp. For a given application, the direction and

magnitude of the output current should be calculated or

measured and checked against the SOA curves. This is

simple for resistive loads but more complex for reactive

and EMF generating loads. The following guidelines may

save extensive analytical efforts.

SUPPLY TO OUTPUT DIFFERENTIAL VOLTAGE, V

SOA

4 AMPLIFIERS LOADED

1 AMPLIFIER LOADED

2 AMPLIFIERS LOADED

3 AMPLIFIERS LOADED

DC, T

DC, T

1

50

10

0.1

10

1

N

o

S

PA162

Quad

Using 3 amplifiers from PA162

as 3 phase motor driver.

FIGURE4.3PhaseInverter

–

+

C

SN

0.01µF

R

SN

10Ω

FIGURE5.R-CSnubber