LM2747

HG

BOOT

LG

PGND

FB

SD

PWGD

FREQ/SYNC

SS/TRACK

SGND

EAO

PGND

1

2

3

4

5

6

7

8

9

10

11

12

13

14

HG

BOOT

LG

PGND

FB

SD

PWGD

FREQ/SYNC

SS/TRACK

SGND

EAO

PGND

Q1

L1

+

LM2747

Clk

Q2

+

LM2747

SNVS370B – MARCH 2006 – REVISED MARCH 2013

www.ti.com

Typical Application

Figure 1. Typical Application Circuit

Connection Diagram

Figure 2. 14-Lead Plastic TSSOP

See PW Package

PIN DESCRIPTION

BOOT (Pin 1) -

Bootstrap pin. This is the supply rail for the high-side gate driver. When the high-side MOSFET turns on, the

the MOSFET. See MOSFET GATE DRIVERS in the APPLICATION INFORMATION section for more details on

how to select MOSFETs.

LG (Pin 2) -

Low-gate drive pin. This is the gate drive for the low-side N-channel MOSFET. This signal is interlocked with the

high-side gate drive HG (Pin 14), so as to avoid shoot-through.

PGND (Pins 3, 13) -

Power ground. This is also the ground for the low-side MOSFET driver. Both the pins must be connected together

on the PCB and form a ground plane, which is usually also the system ground.

SGND (Pin 4) -

Signal ground. It should be connected appropriately to the ground plane with due regard to good layout practices in

switching power regulator circuits.

Supply rail for the control sections of the IC.

PWGD (Pin 6) -

voltage source through a pull-up resistor. Choose the pull-up resistor so that the current going into this pin is kept

below 1 mA. A recommended value for the pull-up resistor is 100 k

Ω for most applications. The voltage on this pin

is thus pulled low under output undervoltage or overvoltage fault conditions and also under input UVLO.

Current limit threshold setting pin. This sources a fixed 40 µA current. A resistor of appropriate value should be

connected between this pin and the drain of the low-side MOSFET (switch node). The minimum value for this

resistor is 1 k

Ω.

2

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