Step-Down Controllers with Prebias Startup,

Lossless Sensing, Synchronization, and OVP

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11

Pin Description (continued)

PIN

MAX8543

MAX8544

NAME

FUNCTION

13

16

LX

Inductor Connection

14

17

DH

High-Side MOSFET Gate-Driver Output. Connect DH to the gate of the high-side

external MOSFETs. DH is pulled low in shutdown.

15

18

BST

Boost Capacitor Connection. Connect a 0.1µF or larger ceramic capacitor from BST to

LX. BST provides power for the high-side MOSFET gate drive.

16

19

FSYNC

Frequency Set and Synchronization. Connect a resistor from FSYNC to GND to set the

switching frequency or drive with a clock signal to synchronize between 160kHz and

1.2MHz. See the Switching Frequency and Synchronization section.

—

1

ILIM2

Connect a resistor from ILIM2 to ground to set the overcurrent threshold. See the

Setting the Current Limits section.

—

10

MODE

Current-Limit Operating-Mode Selection. Connect MODE to VL for latch-off current limit

or connect to GND for automatic-recovery current limit with the MAX8544. The MAX8543

always uses automatic-recovery current limit.

—11

POK

Power-OK. POK is an open-drain output that is high impedance when the output is

above 91% of its nominal regulation voltage. POK is pulled low when the output is out

of regulation and when the part is in shutdown. To use POK as a logic-level signal,

connect a pullup resistor from POK to the logic supply.

—

20

SYNCO

Synchronization Output. Provides a clock output that is 180° out of phase with the rising

edge of DH for out-of-phase synchronization of another MAX8544.