UC3845N View Datasheet(PDF) - Motorola => Freescale

Part Name

Description

Manufacturer

UC3845N

High Performance Current Mode Controllers

Motorola => Freescale 

UC3844, 45 UC2844, 45

Figure 15. Representative Block Diagram

VCC

VCC 7(12)

Vref

8(14)

R

2.5V

RT

R

Internal

Bias

4(7)

CT

Voltage Feedback

Input

2(3)

Output

Compensation

1(1)

Oscillator

+

1.0mA

+

–

Error

Amplifier

2R

R

Reference

+

36V

Regulator

+

VCC – +

UVLO –

3.6V + – Vref

– UVLO

TQ

–

+

1.0V

S

Q

R PWM

Latch

Current Sense

Comparator

VC

7(11)

Output

6(10)

Power Ground

5(8)

Current Sense Input

3(5)

Gnd 5(9)

+

–

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

=

Sink Only

Positive True Logic

Vin

Q1

RS

Capacitor CT

Latch

‘‘Set’’ Input

Output/

Compensation

Current Sense

Input

Latch

‘‘Reset’’ Input

Output

Figure 16. Timing Diagram

Large RT/Small CT

Small RT/Large CT

8

MOTOROLA ANALOG IC DEVICE DATA

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