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LT1738

Slew Rate Controlled Ultralow Noise DC/DC Controller

Linear Technology 

LT1738

PI FU CTIO S

VC (Pin 12): The compensation pin is used for frequency

compensation and current limiting. It is the output of the

error amplifier and the input of the current comparator.

Loop frequency compensation can be performed with an

RC network connected from the VC pin to ground. The

voltage on VC is proportional to the switch peak current.

The normal range of voltage on this pin is 0.25V to 1.27V.

However, during slope compensation the upper clamp

voltage is allowed to increase with the compensation.

During a short-circuit fault the VC pin will be discharged to

ground.

TEST CIRCUITS

5pF

CAP

20mA

IN5819

GATE

ZVN3306A

2

10 –+

5pF

CAP

0.9A

IN5819

GATE

CS

Si4450DY

0.1

10 –+

1738 F01a

1738 F01b

Figure 1a. Typical Test Circuitry Figure 1b. Test Circuit for Slew

BLOCK DIAGRA

100k

NFB 10

+

NEGATIVE

FEEDBACK

– AMP

50k

SHDN VIN

14 17

REGULATOR

VREG

FB 9

VC 12

+

1.25V

–

ERROR

+ AMP

V5

RCSL RVSL

5

15 16

TO

DRIVERS

SLEW

CONTROL

SS 13

RT 8

CT 7

OSCILLATOR

6

SYNC

COMP

SQ

FF

R

SENSE

AMP

SUB

11

GND

3 GCL

2 CAP

1 GATE

20 PGND

4 CS

1738 BD

8

1738fa

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