Compact 600 mA, 3 MHz, Step-Down

Converter with Output Discharge

Data Sheet

ADP2109

Rev. B

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FEATURES

Peak efficiency: 95%

Discharge switch function

Fixed frequency operation: 3 MHz

Typical quiescent current: 18 μA

Maximum load current: 600 mA

Input voltage: 2.3 V to 5.5 V

Uses tiny multilayer inductors and capacitors

Current mode architecture for fast load and line transient

response

100% duty-cycle low dropout mode

Internal synchronous rectifier

Internal compensation

Internal soft start

Current overload protection

Thermal shutdown protection

Shutdown supply current: 0.2 μA

5-ball WLCSP

Supported by ADIsimPower™ design tool

APPLICATIONS

PDAs and palmtop computers

Wireless handsets

Digital audio, portable media players

Digital cameras, GPS navigation units

GENERAL DESCRIPTION

The ADP2109 is a high efficiency, low quiescent current step-

down dc-to-dc converter with an internal discharge switch that

allows automatic discharge of the output capacitor in an ultra-

small 5-ball WLCSP package.

The total solution requires only three tiny external components.

It uses a proprietary high speed current mode and constant

frequency pulse-width modulation (PWM) control scheme for

excellent stability, and transient response. To ensure the longest

battery life in portable applications, the ADP2109 has a power

save mode that reduces the switching frequency under light

load conditions.

The ADP2109 runs on input voltages of 2.3 V to 5.5 V, which

allow for single lithium or lithium polymer cell, multiple alkaline

or NiMH cells, PCMCIA, USB, and other standard power

sources. The maximum load current of 600 mA is achievable

across the input voltage range.

The ADP2109 is available in fixed output voltages of 1.8 V, 1.5 V,

1.2 V, and 1.0 V. All versions include an internal power switch

and synchronous rectifier for minimal external part count and

high efficiency. The ADP2109 has an internal soft start and internal

compensation. During logic-controlled shutdown, the input is

disconnected from the output and the ADP2109 draws less than

1 μA from the input source.

Other key features include undervoltage lockout to prevent deep

battery discharge and soft start to prevent input current overshoot

at startup. The ADP2109 is available in a 5-ball WLCSP.

A similar converter, the ADP2108, provides the same features

and operations as the ADP2109 without the discharge switch

and is available in both WLCSP and TSOT packages with

additional output voltages.

TYPICAL APPLICATIONS CIRCUIT

1.0V TO 1.8V

10µF

1µH

4.7µF

2.3V TO 5.5V

ON

OFF

ADP2109

GND

VIN

EN

SW

FB

Figure 1.