RT7296C

Copyright © 2015 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

DS7296C-00

May

2015

www.richtek.com

3

Function Block Diagram

+

-

UV

Comparator

Oscillator

0.4V

Internal

Regulator

Shutdown

Comparator

BOOT

GND

SW

FB

EN/SYNC

HS Switch

Current

Comparator

+

-

EA

0.807V

Power

Stage &

Deadtime

Control

+

-

1.4V

+

Slope

Compensation

LS Switch

Current

Comparator

UVLO

Logic &

Protection

Control

BOOT

UVLO

Current

Sense

Current

Sense

PVCC

SS

50pF

1pF

400k

11µA

VIN

Operation

Under Voltage Lockout Threshold

The IC includes an input Under Voltage Lockout

Protection (UVLO). If the input voltage exceeds the

UVLO rising threshold voltage (3.9V), the converter

resets and prepares the PWM for operation. If the input

voltage falls below the UVLO falling threshold voltage

(3.25V) during normal operation, the device stops

switching. The UVLO rising and falling threshold

voltage includes a hysteresis to prevent noise caused

reset.

Chip Enable

The EN pin is the chip enable input. Pulling the EN pin

low (<1.1V) will shutdown the device. During shutdown

mode, the RT7296C’s quiescent current drops to lower

than 1

A. Driving the EN pin high (>1.6V) will turn on

the device.

Operating Frequency and Synchronization

The internal oscillator runs at 1400kHz (typ.) when the

EN/SYNC pin is at logic-high level (>1.6V). If the EN

pin is pulled to low-level over 8μs, the IC will shut

down. The RT7296C can be synchronized with an

external clock ranging from 300kHz to 3MHz applied to

the EN/SYNC pin. The external clock duty cycle must

be from 20% to 80% with logic-high level = 2V and

logic-low level = 0.8V.

Internal Regulator

The internal regulator generates 5V power and drive

internal circuit. When VIN is below 5V, PVCC will drop

with VIN. A capacitor (>0.1

F) between PVCC and

GND is required.

Soft-Start Function

The RT7296C provides external soft-start function. The

soft-start function is used to prevent large inrush

current while converter is being powered-up. The