4

LTC3426

3426fa

PI FU CTIO S

SW (Pin 1): Switch Pin. Connect inductor between SW and

Keep these PCB trace lengths as short and wide as

possible to reduce EMI and voltage overshoot. If the

inductor current falls to zero, an internal 100

Ω antiringing

GND (Pin 2): Signal and Power Ground. Provide a short

direct PCB path between GND and the (–) side of the output

capacitor(s).

Connect resistor divider tap to this pin. The output voltage

can be adjusted from 2.5V to 5V by:

V

R

R

⎛

⎝⎜

⎞

⎠⎟

122

1

1

2

.•

SHDN (Pin 4): Logic Controlled Shutdown Input.

SHDN = High: Normal free running operation

SHDN = Low: Shutdown, quiescent current < 1

µA

pull-up resistor.

BLOCK DIAGRA

Figure 1

4

SHUTDOWN AND

SOFT-START

1.22V

REFERENCE

RAMP

GENERATOR

1.2MHz

OSCILLATOR

3426 F01

PWM LOGIC

AND DRIVER

Σ

–

+

3

FB

FB

SHDN

SW

A1

–

+

A2

R2 (EXTERNAL)

R1 (EXTERNAL)

0.02

Ω

1

GND

2

6

COMPARATOR

5