5

LT1610

tion network must be connected to this pin, either internal

(COMP pin) or external series RC to ground. 220k

Ω/

220pF typical value.

FB (Pin 2): Feedback Pin. Reference voltage is 1.23V.

Connect resistive divider tap here. Minimize trace area at

SHDN (Pin 3): Shutdown. Ground this pin to turn off

device. Tie to 1V or more to enable.

PGND (Pin 4): Power Ground. Tie directly to local ground

plane.

SW (Pin 5): Switch Pin. Connect inductor/diode here.

Minimize trace area at this pin to keep EMI down.

GND (Pin 7): Signal Ground. Carries all device ground

current except switch current. Tie to local ground plane.

pin, or let float if external compensation is used. Output

capacitor must be tantalum if COMP pin is used for com-

pensation.

BLOCK DIAGRA

FB

FB

BIAS

R5

40k

1.7MHz

OSCILLATOR

RAMP

GENERATOR

FF

S

RQ

0.15

Ω

–

+

COMP

4

7

3

8

5

6

1

–

+

A = 3

SW

GND

Q1

Q2

× 10

Q3

PGND

A2

1610 F02

SHDN

SHUTDOWN

ENABLE

COMPARATOR

DRIVER

R6

40k

R3

30k

R2

(EXTERNAL)

R4

140k

R1

(EXTERNAL)

–

+

A1

2

Σ

Figure 2. LT1610 Block Diagram