SA51 datasheet(4/4 Pages) APEX

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APEX MICROTECHNOLOGY CORPORATION • 5980 NORTH SHANNON ROAD • TUCSON, ARIZONA 85741 • USA • APPLICATIONS HOTLINE: 1 (800) 546-2739

This data sheet has been carefully checked and is believed to be reliable, however, no responsibility is assumed for possible inaccuracies or omissions. All speciﬁcations are subject to change without notice.

OPERATING

CONSIDERATIONS

SA51

GENERAL

Please read Application Note 30 on "PWM Basics". Refer

to Application Note 1 "General Operating Considerations" for

helpful information regarding power supplies, heat sinking

and mounting. Visit www.apexmicrotech.com for design tools

that help automate pwm ﬁlter design and heat sink selection.

The "Application Notes" and "Technical Seminar" sections

contain a wealth of information on speciﬁc types of applica-

tions. Information on package outlines, heat sinks, mounting

hardware and other accessories are located in the "Packages

and Accessories" section. Evaluation Kits are available for most

Apex product models, consult the "Evaluation Kit" section for

details. For the most current version of all Apex product data

sheets, visit www.apexmicrotech.com.

PIN DESCRIPTION

VCC - is the low voltage supply for powering internal logic and

drivers for the lowside and highside MOSFETS. The supplies

for the highside drivers are derived from this voltage.

S - is the higher voltage H-bridge supply. The MOSFETS

obtain the output current from this supply pin. The voltage on

this pin is limited to +80V by the drive IC. The MOSFETS are

rated at 100 volts. Proper by-passing to GND with sufﬁcient

capacitance to suppress any voltage transients, and to ensure

removing any drooping during switching, should be done as

close to the pins on the hybrid as possible.

A OUT - is the output pin for one half of the bridge. When

the PWM input is high, this output will be pulled up to Vs.

B OUT - is the output pin for the other half of the bridge. When

the PWM input is low, this output will be pulled up to Vs.

RSENSE - This is the common connection for the bottom of

the bridge. This can have a sense resistor connected to the Vs

return ground for current limit sensing, or can be connected

directly to ground. The maximum voltage on this pin is ±2 volts

with respect to GND.

GND - is the return connection for the input logic and Vcc.

PWM INPUT - is a TTL compatible input pin for providing the

PWM signal to modulate the output switches. The duty cycle

can be between 0% (DC low) and 100% (DC high).

DISABLE INPUT - is a TTL compatible input for providing

a shutdown signal to the hybrid for disabling all four switches

in the bridge regardless of the PWM input level. A digital 1

disables, a digital 0 enables.

TYPICAL SYSTEM OPERATION

Below is a diagram of a typical application of the SA51. The

design Vcc voltage is +12 volts and should have a low ESR

bypass capacitor such as a tantalum electrolytic. The PWM

and DISABLE signals are typically provided by some type of

microprocessor control. The PWM signal will be a TTL signal

with a pulse frequency required by the system, and pulse duty

cycles according to the required direction/speed. A 0% duty

cycle (continuous TTL low) will mean full voltage to the motor

in one direction. A 100% duty cycle (continuous TTL high) will

mean full voltage to the motor in the other direction. A 50%

duty cycle will hold the motor at 0 RPM.

Current sensing is done in this case by a 0.1 ohm sense

resistor to sense current from either leg of the bridge. It is

important to make the high current traces as wide as possible

to keep inductance down. The storage capacitor connected

to the +Vs and the hybrid GND should be large enough to

provide the high energy pulse without the voltage sagging

too far. The storage capacitor should be a low ESR ceramic

capacitor or large polypropylene capacitor. Mount capacitor

as close to the hybrid as possible. The connection between

GND and the +Vs return should not be carrying any motor

current. The sense resistor signal is common mode ﬁltered as

necessary to feed the limiting circuitry for the microprocessor.

This application will allow full four quadrant torque control for

a closed loop servo system.

A snubber network is usually required, due to the inductance

in the power loop. It is important to design the snubber network

to suppress any positive spikes above +V

S and negative spikes

below -2V with respect to Pin 5 (GND) of the hybrid.

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