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

SA50CE

4

SA50CEU

GENERAL

Please read Application Note 30 on "PWM Basics".

Refer to Application Note 1 "General Operating Con-

siderations" for helpful information regarding power

supplies, heat sinking and mounting.Visit www.Cirrus.

com for design tools that help automate pwm filter de-

sign and heat sink selection. The "Application Notes"

and "Technical Seminar" sections contain a wealth of

information on specific types of applications.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 Precision Power product models, consult

the "Evaluation Kit" section for details. For the most

current version of all Apex Precision Power product

data sheets, visit www.Cirrus.com.

PINDESCRIPTION

V

logic and drivers for the lowside and highside

MOSFETS.The supplies for the highside drivers

are derived from this voltage.

V

FETS obtain the output current from this supply

pin. 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. Increas-

ing the input voltage causes increasing duty cycle at

this output.

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

Decreasing the input voltage causes increasing duty

cycles at this point.

RSENSE A - This is the connection for the bottom of the A

half bridge. This can have a sense resistor connected

to the V

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 V

RSENSE B - This is the connection for the bottom of the B

half bridge. This can have a sense resistor connection

to the V

be connected directly to ground. The maximum voltage

on this pin is ±2 volts with respect to GND.

INPUT - is an analog input for controlling the PWM pulse width

of the bridge. A voltage higher than V

greater than 50% duty cycle pulses out of A OUT. A

voltage lower than V

duty cycle pulses out of B OUT.

TYPICALSYSTEMOPERATION

This is a diagram of a typical application of the SA50CE.

The design Vcc voltage is +12 volts.V

with a good low ESR ceramic capacitor. A higher ESR bulk

capacitor, such as a tantalum electrolytic, may be used ex-

ternally in parallel. The analog input can be an analog speed

control voltage from a potentiometer, other analog circuitry or

by microprocessor and a D/A converter.This analog input gets

pulled by the current control circuitry in the proper direction

to reduce the current flow in the bridge if it gets too high. The

gain of the current control amplifier will have to be set to obtain

the proper amount of current limiting required by the system.

Current sensing is done in this case by a 0.1Ω sense resistor

to sense the current from both legs of the bridge separately. It

is important to make the high current traces as big as possible

to keep inductance down. The storage capacitor connected to

the V

the high energy pulse without the voltage sagging too far. A

low ESR capacitor will be required. Mount capacitor as close

to the hybrid as possible. The connection between GND and

the V

sense resistor signal is common mode filtered as necessary

to feed the limiting circuitry. 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

below –2V with respect to pin 7 (GND).

SA50CE

+12V

Vcc

+VS

+VS

CURRENT CONTROL

RSENSE B

RSENSE A

SENSE

RESISTORS

0.1Ω

1000pF

200V

100Ω

2W

SNUBBER NETWORK

6.8μF

100V

POLY

MYLAR

GND

GND

R

R

RIN

RIN

Rf

+12V

+12V

RDIVIDE

RDIVIDE

(VCC÷2)

RDIVIDE = 2X Rf

ANALOG

INPUT

NO OUTPUT

SWITCHING

CURRENT

MOTOR A

3

6

8

7

MOTOR B

MOTOR

5

1

2

4

INPUT

22μF