RT7248 datasheet(3/15 Pages) RICHTEK

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RT7248

DS7248-01

September 2012

www.richtek.com

is a registered trademark of Richtek Technology Corporation.

Function Block Diagram

Comparator

Oscillator

Foldback

Control

0.4V

Internal

Regulator

2.5V

Shutdown

Comparator

Current Sense

Amplifier

BOOT

VIN

GND

COMP

VA VCC

6µA

Slope Comp

Current

Comparator

0.923V

1.2V

Lockout

Comparator

VCC

Error Amp

150m

130m

RSENSE

Operation

Shutdown Comparator

Activate internal regulator once EN input level is larger

than the target level. Force IC to enter shutdown mode

when the EN input level is lower than 0.4V.

Internal Regulator

Provide internal power for logic control and switch gate

drivers.

Lockout Comparator

Activate the Current Comparator, release lock-out logic,

and enable the switches as EN input level is larger than

lockout voltage. Otherwise, the switches still locks 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 Amp

The output voltage COMP of the error amplifier is adjusted

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. Then, it controls

the switches by comparing this signal with the COMP

voltage.

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