RT2652

2

DS2652-00

November 2012

www.richtek.com

©

Copyright

2012 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

Function Block Diagram

Functional Pin Description

Pin No.

Pin Name

Pin Function

1

EN

Enable Control Input. Pull high to turn on. Do not float.

2, 3

VIN

Power Input. Decouple this pin to GND with a 22

μF ceramic capacitor at least.

4, 6

AGND

Analog Ground.

5

FB

Feedback Voltage Input. This pin receives the feedback voltage from an external

resistive divider connected across the output.

7, 8

LX

Power MOSFET Switch Node. Connect this pin to the inductor.

9, 10,

11 (Exposed Pad)

PGND

Power Ground. The exposed pad must be soldered to a large PCB and

connected to GND for maximum power dissipation.

Operation

The RT2652 is a monolithic, constant-frequency, current

mode step-down DC/DC converter. During normal

operation, the internal high side MOSFET is turned on at

the beginning of each cycle. Current in the inductor

increases until the peak inductor current reaches the value

defined by the internal error amplifier. The error amplifier

adjusts the voltage of its output by comparing the feedback

signal from a resistor divider on the FB pin with an internal

0.6V reference. When the load current increases, it causes

a reduction in the feedback voltage relative to the reference.

The error amplifier raises its output voltage until the average

inductor current matches the new load current. When the

high side MOSFET turns off, the synchronous power

switch (N-MOSFET) turns on until either the bottom current

limit is reached or the beginning of the next cycle. The

operating frequency is set by the internal oscillator at

1.2MHz. In VIN larger than 6V condition, the high side

MOSFET is turned off and the low side MOSFET is

switched on until either the VIN over voltage condition is

cleared or the low side MOSFET's current limit is reached.

In FB larger than 1.05V condition, the high side MOSFET

turns off, and the low side MOSFET turns on, and IC is

latched until restarted.

Driver

Control Logic

LX

PGND

OSC

Slope

Comp.

EN

FB

Output

Clamp

VIN

EN

N-MOSFET Limit

NISEN

ISEN

OC Limit

0.6V

SS

EA

UV

0.2V

POR

OTP

AGND