Compact, 800 mA, 3 MHz,

Step-Down DC-to-DC Converter

Data Sheet

ADP2138/ADP2139

Rev. C

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FEATURES

Input voltage: 2.3 V to 5.5 V

Peak efficiency: 95%

3 MHz fixed frequency operation

Typical quiescent current: 24 μA

Very small solution size

6-lead, 1 mm × 1.5 mm WLCSP package

Fast load and line transient response

100% duty cycle low dropout mode

Internal synchronous rectifier, compensation, and soft start

Current overload and thermal shutdown protections

Ultralow shutdown current: 0.2 μA (typical)

Forced PWM and automatic PWM/PSM modes

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 ADP2138 and ADP2139 are high efficiency, low quiescent

current, synchronous step-down dc-to-dc converters. The

ADP2139 has the additional feature of an internal discharge

switch. The total solution requires only three tiny external

components. When the MODE pin is set high, the buck

regulator operates in forced PWM mode, which provides low

peak-to-peak ripple for power supply noise sensitive loads at

the expense of light load efficiency. When the MODE pin is set

low, the buck regulator automatically switches operating modes,

depending on the load current level. At higher output loads, the

buck regulator operates in PWM mode. When the load current

falls below a predefined threshold, the regulator operates in power

save mode (PSM), improving light load efficiency.

The ADP2138/ADP2139 operate on input voltages of 2.3 V to

5.5 V, which allows for single lithium or lithium polymer cell,

multiple alkaline or NiMH cell, PCMCIA, USB, and other

standard power sources. The maximum load current of 800 mA

is achievable across the input voltage range.

The ADP2138/ADP2139 are available in fixed output voltages of

3.3 V, 3.0 V, 2.8 V, 2.5 V, 1.8 V, 1.5 V, 1.2 V, 1.0 V, and 0.8 V. All

versions include an internal power switch and synchronous rect-

ifier for minimal external part count and high efficiency. The

ADP2138/ADP2139 have internal soft start and they are internally

compensated. During logic controlled shutdown, the input is

disconnected from the output and the ADP2138/ADP2139

draw 0.2 μA (typical) from the input source.

Other key features include undervoltage lockout to prevent deep

battery discharge, and soft start to prevent input current over-

shoot at startup. The ADP2138/ADP2139 are available in a 6-ball

wafer level chip scale package (WLCSP).

TYPICAL APPLICATIONS CIRCUIT

ON

OFF

FORCE

PWM

AUTO

VIN

SW

EN

MODE

GND

VOUT

ADP2138/

ADP2139

4.7µF

4.7µF

2.3V TO 5.5V

1.0µH

Figure 1.