LP6255-02

Feb.-2014

www.lowpowersemi.com

Page 2 of 10

Preliminary Datasheet

LP6255

Functional Pin Description

Pin

Name

Description

1

COMP

Compensation pin. The loop compensation network should be connected between this pin

and the GND pin.

2

FB

Feedback input. Connect to an external resistive voltage divider from the output to FB to set

3

SLP

Slope compensation is programmed by an external resistor between SLP and the GND.

7,18

NC

No Connector. There should not connect ground or VIN to it. Leaving it float is OK.

4,13

VREF

Internal bias supply. Decouple with a 10uF ceramic capacitor as close to the pin as possible.

6

EN

Chip enable pin. If the EN pin is below 1V, the regulator is in the shutdown mode with all

functions disabled. If the EN pin voltage is above 2.2V, the startup sequence begins. EN

exceeds 2.2 V and flows through the external EN resistors to provide hysteresis. The EN pin

should not be left floating.

8

MODE

Switching mode selection pin. When MODE pin voltage is greater than 1.4 V, diode

emulation mode threshold, forced PWM mode is enabled, allowing current to flow in either

direction through the high-side N-channel MOSFET switch. If the MODE pin is below 0.1V or

grounded, the controller still operates in diode emulation mode, but the skip cycle comparator

will not be triggered in normal operation, this enables pulse skipping operation at light load.

9

RT

The internal oscillator frequency is programmed by an external resistor between RT and the

GND. The internal oscillator can be synchronized to an external clock by applying a positive

pulse signal into this pin.

10

SS

Soft start pin. Connect a capacitor to this pin. The capacitor is charged with a constant

current.

5,11

GND

Power Ground pin.

12

LDR

Pin for driving external N-Channel MOS which cooperates with external NMOS.

14

VOUT

This pin needs connection to output node.

15

LX

Connect inductor between LX and VIN. Make these PCB trace lengths as short and wide as

possible to reduce EMI and voltage overshoot.

16

HDR

Pin for driving external N-Channel MOS which work as switch tube.

17

BST

Bootstrap pin to power the MOS driver. Connect a capacitor between this pin and LX pin.

19

CS

Connect to negative-side of current sense resistor as voltage detective pin cooperating with

VIN pin.

20

VIN

Voltage supply pin.