UC3842A, 43A UC2842A, 43A

7

MOTOROLA ANALOG IC DEVICE DATA

+

–

Sink Only

Positive True Logic

=

RS

+

Internal

Bias

Reference

Regulator

Oscillator

S

R

Q

–

Vref

UVLO

3.6V

36V

VCC

7(12)

Q1

Vin

VCC

VC

7(11)

6(10)

5(8)

3(5)

+

1.0mA

Error

Amplifier

1(1)

2(3)

4(7)

8(14)

5(9)

Gnd

Output

Compensation

Voltage Feedback

Input

RT

CT

Vref

–

–

PWM

Latch

Current Sense

Comparator

R

R

Power Ground

Current Sense Input

2R

R

1.0V

Pin numbers in parenthesis are for the D suffix SO–14 package.

Q

T

+

–

+

+

–

+

–

+

VCC

UVLO

Output

2.5V

Figure 17. Representative Block Diagram

Output/

Compensation

Current Sense

Input

Latch

‘‘Reset’’ Input

Output

Capacitor CT

Latch

‘‘Set’’ Input

Large RT/Small CT

Small RT/Large CT

Figure 18. Timing Diagram