UC3842B, 43B UC2842B, 43B

7

MOTOROLA ANALOG IC DEVICE DATA

PIN FUNCTION DESCRIPTION

Pin

Fi

Di

i

8–Pin

14–Pin

Function

Description

1

1

Compensation

This pin is the Error Amplifier output and is made available for loop compensation.

2

3

Voltage

Feedback

This is the inverting input of the Error Amplifier. It is normally connected to the switching power

supply output through a resistor divider.

3

5

Current

Sense

A voltage proportional to inductor current is connected to this input. The PWM uses this

information to terminate the output switch conduction.

4

7

RT/CT

The Oscillator frequency and maximum Output duty cycle are programmed by

connecting resistor RT to Vref and capacitor CT to ground. Operation to 500 kHz

is possible.

5

Gnd

This pin is the combined control circuitry and power ground.

6

10

Output

This output directly drives the gate of a power MOSFET. Peak currents up to 1.0 A are sourced

and sunk by this pin.

7

12

VCC

This pin is the positive supply of the control IC.

8

14

Vref

This is the reference output. It provides charging current for capacitor CT through resistor RT.

8

Power

Ground

This pin is a separate power ground return that is connected back to the power source. It is used

to reduce the effects of switching transient noise on the

control circuitry.

11

VC

The Output high state (VOH) is set by the voltage applied to this pin. With a separate power

source connection, it can reduce the effects of switching transient noise on the control circuitry.

9

Gnd

This pin is the control circuitry ground return and is connected back to the power source ground.

2,4,6,13

NC

No connection. These pins are not internally connected.