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Datasheet

BU9000xGWZ series

TSZ02201-0F2F0AG00010-1-2

© 2012 ROHM Co., Ltd. All rights reserved.

04.Jul.2012 Rev.001

www.rohm.co

m

TSZ22111・

・

・

・15・

・

・

・001

GND

LX

VIN

EN

+

-

SHUTDOWN

TSD

ERROR

COMP

FB

Frequency

control

UVLO

VREF

Switching

Control

Logic

and

Gate

Driver

MODE

PWM/PFM

control

B1

1.5～0.47uH

4.7uF

VOUT

2.3～5.5V

VOUT

H

：　ON

L

：　OFF

L

：　PWM/PFM

MODE

H

：　PWM

MODE

A1

B2

A3

A2

B3

EN

●

●

●

●

Block Diagram(s)

●

●

●

●

Description of Block(s)

The BU9000xGWZ are a synchronous step-down DC/DC converter that achieves fast transient response from light load to

heavy load by hysteretic PWM control system and current constant PFM control system.

○

PWM control

BU9000xGWZ operates by hysteretic PWM control. This scheme ensures fast switching, high efficiency, and fast transient

response.

When the output voltage is below the VREF voltage, the error comparator output is low to high and turning on P-channel

MOSFET until above the VREF voltage and minimum on time.

○

PFM control

At light load the regulator and MODE=low, the regulator operates with reduced switching frequency and improves the

efficiency.During PFM operation, the output voltage slightly higher than typical output voltage.

Figure 4. Operation of PFM mode and PWM mode

Figure 3. Block Diagram(s)

PFM

(constant

current)Threshold.

turn

off

Pch

FET

output

PWM

mode

voltage

PFM

Mode

at

Light

Load

PFM

Threshold.

turn

on

PFET

PWM

Mode

at

Moderate

to

Heavy

Loads