Rainbow Electronics MAX1557 - Manual

General Description
The MAX1556/MAX1557 are low-operating-current
(16µA), fixed-frequency step-down regulators. High effi-
ciency, low-quiescent operating current, low dropout,
and minimal (27µA) quiescent current in dropout make
these converters ideal for powering portable devices
from 1-cell Li-ion or 3-cell alkaline/NiMH batteries. The
MAX1556 delivers up to 1.2A; has pin-selectable 1.8V,
2.5V, and 3.3V outputs; and is also adjustable. The
MAX1557 delivers up to 600mA; has pin-selectable 1V,
1.3V, and 1.5V outputs; and is also adjustable.
The MAX1556/MAX1557 contain a low-on-resistance
internal MOSFET switch and synchronous rectifier to
maximize efficiency and dropout performance while
minimizing external component count. A proprietary
topology offers the benefits of a high fixed-frequency
operation while still providing excellent efficiency at
both light and full loads. A 1MHz PWM switching fre-
quency keeps components small. Both devices also
feature an adjustable soft-start to minimize battery tran-
sient loading.
The MAX1556/MAX1557 are available in a tiny 10-pin
TDFN (3mm x 3mm) package.
Applications
PDAs and Palmtop Computers
Cell Phones and Smart Phones
Digital Cameras and Camcorders
Portable MP3 and DVD Players
Hand-Held Instruments
Features
♦ Up to 97% Efficiency
♦ 95% Efficiency at 1mA Load Current
♦ Low 16µA Quiescent Current
♦ 1MHz PWM Switching
♦ Tiny 3.3µH Inductor
♦ Selectable 3.3V, 2.5V, 1.8V, 1.5V, 1.3V, 1.0V, and
Adjustable Output
♦ 1.2A Guaranteed Output Current (MAX1556)
♦ Voltage Positioning Optimizes Load-Transient
Response
♦ Low 27µA Quiescent Current in Dropout
♦ Low 0.1µA Shutdown Current
♦ No External Schottky Diode Required
♦ Analog Soft-Start with Zero Overshoot Current
♦ Small, 10-Pin, 3mm x 3mm TDFN Package
MAX1556/MAX1557
16µA I Q , 1.2A PWM
Step-Down DC-DC Converters
________________________________________________________________ Maxim Integrated Products 1
TOP VIEW
LX
OUT
SHDN 6
7
8
9
10
INP
D1
3
2
1
SS
GND
IN
5
PGND
D2
4
TDFN
MAX1556/
MAX1557
Pin Configuration
Ordering Information
LX
SS
ON
OFF SHDN
GND
INPUT
2.6V TO 5.5V
VOLTAGE
SELECT
OUTPUT
0.75V TO V
IN
PGND
OUT
INP
IN
D1
D2
MAX1556/
MAX1557
Typical Operating Circuit
19-3336; Rev 0; 7/04
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
EVALUATION KIT
AVAILABLE
PART TEMP RANGE PIN-PACKAGE
TOP
MARK
MAX1556ETB -40 °C to +85°C
10 TDFN-EP*
(T1033-1)
ACQ
MAX1557ETB -40 °C to +85°C
10 TDFN-EP*
(T1033-1)
ACR
* EP = Exposed paddle.