LM2743MTCSLASHNOPB datasheet(3/44 Pages) TI2

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BOOT

ISEN

PGND

VCC

PWGD

FREQ

SS/TRACK

SGND

EAO

PGND

LM2743

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SNVS276I – APRIL 2004 – REVISED FEBRUARY 2019

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5 Pin Configuration and Functions

PW Package

14-Pin TSSOP

Top View

Pin Functions

DESCRIPTION

NAME

NO.

BOOT

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

voltage on this pin should be at least one gate threshold above the regulator input voltage VIN to

properly turn on the MOSFET. See MOSFET Gate Drivers for more details on how to select

MOSFETs.

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

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

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

practices in switching power regulator circuits.

VCC

Supply rail for the control sections of the IC.

PWGD

Power Good pin. This is an open drain output, which is typically meant to be connected to VCC or any

other low 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. For most applications a recommended value for the pull-up

resistor is 100 k

Ω. The voltage on this pin is thus pulled low under output under-voltage or over-

voltage fault conditions and also under input UVLO.

ISEN

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).

EAO

Output of the error amplifier. The voltage level on this pin is compared with an internally generated

ramp signal to determine the duty cycle. This pin is necessary for compensating the control loop.

SS/TRACK

Soft-start and tracking pin. This pin is internally connected to the non-inverting input of the error

amplifier during soft-start, and in fact any time the SS/TRACK pin voltage happens to be below the

internal reference voltage. For the basic soft-start function, a capacitor of minimum value 1 nF is

connected from this pin to ground. To track the rising ramp of another power supply’s output, connect

a resistor divider from the output of that supply to this pin as described in Application and

Implementation.

Feedback pin. This is the inverting input of the error amplifier, which is used for sensing the output

voltage and compensating the control loop.

FREQ

Frequency adjust pin. The switching frequency is set by connecting a resistor of suitable value

between this pin and ground. The equation for calculating the exact value is provided in Application

and Implementation, but some typical values (rounded up to the nearest standard values) are 324 k

Ω

for 100 kHz, 97.6 k

Ω for 300 kHz, 56.2 kΩ for 500 kHz, 24.9 kΩ for 1 MHz.

IC shutdown pin. Pull this pin to VCC to ensure the IC is enabled. Connect to ground to disable the IC.

Under shutdown, both high-side and low-side drives are off. This pin also features a precision

threshold for power supply sequencing purposes, as well as a low threshold to ensure minimal

quiescent current.

High-gate drive pin. This is the gate drive for the high-side N-channel MOSFET. This signal is

interlocked with LG (Pin 2) to avoid shoot-through.

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