10/94

Note: Pin numbers refer to PLCC package.

BLOCK DIAGRAM

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Precision Current Control

•

•

•

Controlled Velocity Head Parking

•

Precision Dual Supply Monitor

with Indicator

•

Limit Input to Force Output

Extremes

•

Inhibit Input and UVLO

•

4V to 15V operation

This full-bridge power amplifier is rated for continuous output current of 0.8 Am-

peres and is intended for use in demanding servo applications such as head

positioning for high-density disk drives. The device includes a precision current

sense amplifier that provides accurate control of load current. Current is

sensed with a single resistor in series with the load. The power amplifier has a

very low output saturation voltage and will operate down to 4V supply levels.

Power output stage protection includes current limiting and thermal shutdown.

Auxiliary functions on this device include a dual-input under-voltage compara-

tor, which can monitor two independent supply voltages and force a built-in

head park function when either is below minimum. When activated by either the

UV comparator, or a command at the separate PARK input, the park circuitry

will override the amplifier inputs to convert the power outputs to a programma-

ble constant voltage source which will hold regulation as the supply voltage

falls to below 3.0 Volts. Added features include a POWER OK flag output, a

LIMIT input to force the drive output to its maximum level in either polarity, and

a over-riding INHIBIT input to disable all amplifiers and reduce quiescent sup-

ply current.

This device is packaged in a power PLCC surface mount configuration which

maintains a standard 28-pin outline, but with 7 pins along one edge allocated to

ground for optimum thermal transfer. And is also available in a 24-pin surface

mount SOIC package.

UC3175B

Full-Bridge Power Amplifier

FEATURES

DESCRIPTION

UDG-92054-1