RT7247B datasheet(3/15 Pages) RICHTEK

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RT7247B

DS7247B-01

September 2012

www.richtek.com

is a registered trademark of Richtek Technology Corporation.

Function Block Diagram

Operation

Internal Regulator

Provide internal power for logic control and switch gate

drivers.

Shutdown Comparator

Activate internal regulator once EN input level is higher

than the target level. Force IC to enter shutdown mode

when the EN input level is lower than 0.4V.

Lockout Comparator

Activate the current comparator, release lock-out logic,

and enable the switches as EN input level is higher than

lockout threshold voltage. Otherwise, the switches still

lock out.

Oscillator

The oscillator provides internal clock and controls the

converter's switching frequency.

Foldback Control

Dynamically adjust the internal clock. It provides a slower

frequency as a lower FB voltage.

UV Comparator

As FB voltage is lower than the UV voltage, it will activate

a UV protect scheme.

Error Amplifier

The output voltage COMP of the error amplifier is adjusted

by comparing FB signal with the internal reference voltage

and SS signal.

Current Sense Amplifier

RSENSE detects the peak current of the high side switch.

This signal is amplified by the current sense amplifier and

added with a slope compensation signal. Then, It controls

the switches by comparing this signal with the COMP

voltage.

Comparator

Oscillator

Foldback

Control

0.4V

Internal

Regulator

1.8V

Shutdown

Comparator

Current Sense

Amplifier

BOOT

VIN

GND

COMP

VA VCC

6µA

Slope Comp

Current

Comparator

0.8V

1.2V

Lockout

Comparator

VCC

130m

150m

RSENSE

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