13

SC403B

Pin Descriptions

Pin #

Pin Name

Pin Function

1

FB

Feedback input for switching regulator used to program the output voltage — connect to an external resis-

tor divider from VOUT to AGND.

2

VOUT

Switcher output voltage sense pin — also the input to the internal switch-over between VOUT and VLDO.

The voltage at this pin must be less than or equal to the voltage at the VDD pin.

3

VDD

Bias supply for the IC — when using the internal LDO as a bias power supply, the VDD is the LDO output.

When using an external power supply to bias the IC, the LDO output should be disabled.

4, 30, PAD 1

AGND

Analog ground

5

FBL

Feedback input for the internal LDO — connect to an external resistor divider from VDD to AGND to pro-

gram the LDO output.

6, 9-11,

PAD 2

VIN

Input supply voltage

7

SS

The soft start time is programmed by an internal current source charging a capacitor on this pin.

8

BST

Bootstrap pin — connect a capacitor of at least 100nF from BST to LX to develop the floating supply for the

high-side gate drive.

12

NC

No connection

13

LXBST

LX Boost — connect to the BST capacitor.

23-25, PAD 3

LX

Switching (phase) node

14

NC

No connection

15-22

PGND

Power ground

26

PGOOD

Open-drain power good indicator — high impedance indicates power is good. An external pull-up

resistor is required.

27

ILIM

Current limit sense pin — used to program the current limit by connecting a resistor from ILIM to LXS.

28

LXS

LX sense — connects to R

29

EN/PSV

Enable/power-save input for the switching regulator — connect to AGND to disable the switching regulator.

Float to operate in forced continuous mode (PSAVE disabled). Connect to VDD to operate with PSAVE mode

enabled.

31

TON

On-time programming input — set the on-time by connecting through a resistor to AGND.

32

ENL

Enable input for the LDO — connect ENL to AGND to disable the LDO. Drive with logic signal for logic con-

trol, or program the VIN UVLO with a resistor divider between VIN, ENL, and AGND pins.