UC3842B, UC3843B, UC2842B, UC2843B

www.onsemi.com

7

Sink Saturation

Source Saturation

(Load to Ground)

0

800

0

200

400

600

1.0

2.0

3.0

-2.0

-1.0

0

Figure 14. Output Saturation Voltage

versus Load Current

Figure 15. Output Waveform

Figure 16. Output Cross Conduction

Figure 17. Supply Current versus Supply Voltage

0

0

10

20

30

40

5

10

15

20

25

GND

80

ms Pulsed Load

120 Hz Rate

50 ns/DIV

100 ns/DIV

90%

10%

PIN FUNCTION DESCRIPTION

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

The Oscillator frequency and maximum Output duty cycle are programmed by connecting resistor

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

This pin is the positive supply of the control IC.

8

14

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

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.

2,4,6,1

3

NC

No connection. These pins are not internally connected.