RT7232 datasheet(4/18 Pages) RICHTEK

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RT7231/32/33/34

DS7231/32/33/34-00

March 2013

www.richtek.com

is a registered trademark of Richtek Technology Corporation.

Function Block Diagram

* : VCC pin for TSSOP-14 (Exposed Pad) only.

VS pin for TSSOP-14 (Exposed Pad) only.

GND pin for TSSOP-14 (Exposed Pad) only.

PGOOD pin for TSSOP-14 (Exposed Pad) and WDFN-10L 3x3 only.

Operation

The RT7231/32/33/34 is a synchronous step-down

converter with advanced constant on-time control mode.

Using the ACOTTM control mode can reduce the output

capacitance and provide fast transient response. It can

minimize the component size without additional external

compensation network.

Power Good

(for TSSOP-14 (Exposed Pad) and WDFN-10L 3x3 only)

After soft-start is finished, the power good function will be

activated. When the FB is activated, the PGOOD will

become an open-drain output. If the FB is below, the

PGOOD pin will be pulled low.

Internal Regulator

The regulator provides 5V power to supply the internal

control circuit. Connecting a 1

μF ceramic capacitor for

decoupling and stability is required.

Soft-Start

In order to prevent the converter output voltage from

overshooting during the startup period, the soft-start

function is necessary. The soft-start time is adjustable

and can be set by an external capacitor.

Current Protection

The inductor current is monitored via the internal switches

in cycle-by-cycle. Once the output voltage drops under

UV threshold, the device will enter latch mode for TSSOP-

14 (Exposed Pad), and hiccup mode for WDFN-10L 3x3.

UVLO Protection

To protect the chip from operating at insufficient supply

voltage, the UVLO is needed. When the input voltage of

VCC is lower than the UVLO falling threshold voltage, the

device will be latch-off.

Output Discharge Control

(for TSSOP-14 (Exposed Pad) only)

When EN pin is low, the RT7231/32 will discharge the

output with an internal 50

Ω MOSFET connected between

VOUT to GND pin.

Thermal Shutdown

When the junction temperature exceeds the OTP

threshold value, the IC will shut down the switching

operation. Once the junction temperature cools down and

is lower than the OTP lower threshold, the converter will

automatically resume switching

VCC*

POR &

Reg

Driver

BOOT

VREG5

Control

VBIAS

On-Time

VIN

Min.

Off-Time

Ripple

Gen.

VREF

Comparator

PGND

VREG5

2µA

VREG5

UV & OV

VS*

VIN

Comparator

0.9 x VREF

PGOOD*

GND*

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