7

© 2008 Semtech Corp.

SC471/SC471A

www.semtech.com

POWER MANAGEMENT

Pin Descriptions

Pin

Pin Name

Pin Function

1

LX

Switching (phase) node.

2

BST

Boost capacitor connection for high-side gate drive.

3

VCC

5V power input for the internal circuits and gate drive outputs.

4

DL

Gate drive output for the low-side external MOSFET.

5

GND

Power ground. This is the return point for the DL driver output, and the reference point for the

ILIM and zero cross circuits.

6RTN

Return or analog ground for the FB input and FB resistor divider . Connect to GND directly at the

IC. All feedback components should connect to this ground.

7

D1

Drain of second internal MOSFET which is controlled by G1.

8

D0

Drain of first internal MOSFET which is controlled by G0.

9FB

Feedback sense point. The FB threshold is 0.75V; the resistor divider ratio between VOUT and

FB sets the output voltage. This ratio can be modified using the G0/G1 inputs to switch resistors

in/out at D0/D1.

10

VOUT

Output voltage sense point for determining On-Time.

11

PGOOD

Open-drain power good indicator - a high impedance indicates power is good - an external pull-up

resistor is required.

12

EN

Enable input - connect EN to RTN to disable the SC471/A.

13

ILIM

Current limit sense point — to program the current limit connect a resistor from ILIM to

LX or to a current sense resistor.

14

G0

Control input for the D0 MOSFET. A logic high (low) energizes the D0 MOSFET on the SC471

(SC471A), pulling D0 to ground.

15

G1

Control input for the D1 MOSFET. A logic high (low) energizes the D1 MOSFET on the SC471

(SC471A), pulling D1 to ground.

16

DH

Gate drive output for the high-side external MOSFET.

TPAD

Mounting pad. Not connected internally - connect to system (power) ground plane through prefer-

ably one large via or multiple smaller vias.