High-Accuracy Step-Down Controller

with Synchronous Rectifier for CPU Power

_______________________________________________________________________________________

5

______________________________________________________________Pin Description

SKIP

Disables pulse-skipping mode when high. Connect to GND for normal use. Don’t leave

SKIP unconnected.

With

SKIP grounded, the device will automatically change from pulse-skipping operation to full PWM opera-

tion when the load current exceeds approximately 30% of maximum.

16

DH

High-Side Gate-Drive Output. Normally drives the main buck switch. DH is a floating driver output that swings

from LX to BST, riding on the LX switching-node voltage.

15

LX

Switching Node (inductor) Connection. Can swing 2V below ground without hazard.

14

BST

Boost Capacitor Connection for high-side gate drive (0.1µF)

13

DL

Low-Side Gate-Drive Output. Normally drives the synchronous-rectifier MOSFET. Swings 0V to VL.

NAME

FUNCTION

1

SS

Soft-Start Timing Capacitor Connection. Ramp time to full current limit is approximately 1ms/nF.

2

PIN

3

REF

Reference Voltage Output. Bypass to GND with 0.33µF minimum.

7

FB

Feedback Input. Regulates at FB = 1.6V. Connect FB to a resistor divider to set the output voltage.

6

SHDN

MOSFET). Tie

SHDN to V+ for automatic start-up.

5

SYNC

Oscillator Synchronization and Frequency Select. Tie to GND or VL for 150kHz operation; tie to REF for

300kHz operation. A high-to-low transition begins a new cycle. Drive SYNC with 0V to 5V logic levels (see the

4

GND

Low-Noise Analog Ground and Feedback Reference Point

12

PGND

Power Ground

11

VL

5V Internal Linear-Regulator Output. VL is also the supply voltage rail for the chip. VL is switched to the out-

up to 5mA for external loads.

10

V+

Battery Voltage Input (4.5V to 30V). Bypass V+ to PGND close to the IC with a 0.1µF capacitor. Connects to a

linear regulator that powers VL.

9

CSL

Current-Sense Input, low side

8

CSH

Current-Sense Input, high side. Current-limit level is 100mV referred to CSL.