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AIC3842CS

Current-Mode PWM Controller

Analog Intergrations 

AIC3842

n BLOCK DIAGRAM

VCC 7

ZD

5 34V

GND

UVLO

S/R

5V

REF

Internal Bias

4

RT/CT

2

VFB

1

COMP

3

ISENSE

2.50V

OSC

Error Amp.

D1 D2 R2

VREF

Good

Logic

PWM

S

Latch

R

Z1 Current

1V Sense

comparator

8

Q1

6

Q2

VREF

5V/50mA

OUTPUT

n PIN DESCRIPTIONS

PIN 1: COMP

- This pin is the error amplifier

output and is made available for

loop compensation.

PIN 2: VFB

- This is the inverting input of the

error amplifier. It is normally

connected to the switching

power supply output through a

resistor divider.

PIN 3: ISENSE - A voltage proportional to

inductor current is connected to

this input. The PWM uses this

information to terminate the

output switch conduction.

PIN 4: 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

500KHz is feasible.

PIN 5: GND-

This pin is the combined control

circuitry and power ground.

PIN 6:

OUTPUT- This output directly drives the

gate of a power MOSFET. Peak

currents up to 1A are sourced

and sunk by this pin.

PIN 7: VCC -

This pin is the positive supply of

the control IC.

PIN 8: VREF -

This is the reference output. It

provides charging current for

capacitor CT through resistor RT.

5

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