LM2727 datasheet(2/22 Pages) NSC

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Connection Diagram

20049411

14-Lead Plastic TSSOP

JA = 155˚C/W

NS Package Number MTC14

Pin Description

BOOT (Pin 1) - Supply rail for the N-channel MOSFET gate

drive. The voltage should be at least one gate threshold

above the regulator input voltage to properly turn on the

high-side N-FET.

LG (Pin 2) - Gate drive for the low-side N-channel MOSFET.

This signal is interlocked with HG to avoid shoot-through

problems.

PGND (Pins 3, 13) - Ground for FET drive circuitry. It should

be connected to system ground.

SGND (Pin 4) - Ground for signal level circuitry. It should be

connected to system ground.

CC (Pin 5) - Supply rail for the controller.

PWGD (Pin 6) - Power Good. This is an open drain output.

The pin is pulled low when the chip is in UVP, OVP, or UVLO

mode. During normal operation, this pin is connected to V

or other voltage source through a pull-up resistor.

ISEN (Pin 7) - Current limit threshold setting. This sources a

fixed 50µA current. A resistor of appropriate value should be

connected between this pin and the drain of the low-side

FET.

EAO (Pin 8) - 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 (Pin 9) - Soft start pin. A capacitor connected between

this pin and ground sets the speed at which the output

voltage ramps up. Larger capacitor value results in slower

output voltage ramp but also lower inrush current.

FB (Pin 10) - This is the inverting input of the error amplifier,

which is used for sensing the output voltage and compen-

sating the control loop.

FREQ (Pin 11) - The switching frequency is set by connect-

ing a resistor between this pin and ground.

SD (Pin 12) - IC Logic Shutdown. When this pin is pulled low

the chip turns off the high side switch and turns on the low

side switch. While this pin is low, the IC will not start up. An

internal 20µA pull-up connects this pin to V

CC.

HG (Pin 14) - Gate drive for the high-side N-channel MOS-

FET. This signal is interlocked with LG to avoid shoot-

through problems.

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