SC1401

© 2000 SEMTECH CORP.

652 MITCHELL ROAD

NEWBURY PARK CA 91320

HIGH PERFORMANCE SYNCHRONOUS BUCK

CONTROLLER WITH LDO FOR PORTABLE

POWER

November 21, 2000

2

Note: All logic level inputs and outputs are open collector TTL compatible.

Pin #

Pin Name

Pin Function

1

SYNC

Oscillator control/synchronization input. Connect to V5V for 300kHz. Connect to

GND for 200kHz. For external clock synchronization in the 240kHz to 350kHz

range. A high-to-low transition causes a new cycle start.

2

SHDN

Logic Low shuts down the switching regulator.

3

FB

Feedback input for the SMPS. FB selects fixed 1.25V output voltage setting

Refer to page 9.

4

VDD1

Supply input from battery (6V to 30V).

5

GND

Low noise analog ground and feedback reference point.

6

CSL

Inverting input to current sense amplifier. Also serves as the feedback input in

fixed output mode.

7

CSH

Non-Inverting input to current sense amplifier. Current limit level is 120mV

referenced to CSL.

8

V5V

5 volt external supply used to power the gate drives, internal control and

reference of the SC1401.

9

DL

Gate drive output for low side synchronous rectifier MOSFET.

10

PGND

Device power ground.

11

PGND

Device power ground.

12

PHASE

Inductor switching node connected to the source of high side MOSFET

and drain of low side MOSFET.

13

DH

Gate drive output for high side N-Channel MOSFET. DH is a floating driver

output driven from the floating voltage across BST to PHASE.

14

BST

Boost capacitor connection for the high side driver.

15

VDD2

Supply voltage input for the linear FET controller.

16

GATEIO

Gate drive output for the linear FET controller.

17

IOS

Sense input voltage for the adjustable voltage linear FET controller.

Refer to page 9.

18

ENABLEIO

Logic low shuts down the linear FET controller.

19

RESET

Active-Low reset output.

20

PSAVE

A logic low enables power saving mode.

PIN DESCRIPTION











 +

•

=

9

8

O

R

R

1

1.25

(SMPS)

V











 +

•

=

6

5

O

R

R

1

1.25

(Linear)

V