Rainbow Electronics MAX1775 - Manual

General Description
The MAX1775 is a dual, step-down DC-DC converter
that generates both the main (+3.3V at over 2A) and
core (+1.8V at up to 1.5A) supplies for a complete
power solution for PDAs, subnotebooks, and other
hand-held devices. The main output is adjustable from
+1.25V to +5.5V. The core output is adjustable from 1V
to 5V. Both switching converters operate at up to
1.25MHz for small external components and use syn-
chronous rectifiers to achieve efficiencies up to 95%.
Operation with up to 100% duty cycle provides the low-
est possible dropout voltage to extend useful battery
life.
The MAX1775 accepts inputs from +2.7V up to +28V,
allowing use with many popular battery configurations as
well as AC-DC wall adapters. Digital soft-start reduces
battery current surges at power-up. Both the main and
core converters have separate shutdown inputs. The
MAX1775 comes in a small 16-pin QSOP package.
The MAX1775 evaluation kit is available to help reduce
design time.
________________________Applications
Hand-Held Computers
PDAs
Internet Access Tablets
POS Terminals
Subnotebooks
Features
♦ Dual, High-Efficiency, Synchronous Rectified
Step-Down Converter
♦ Main Power
Adjustable from +1.25V to +5.5V
Over 2A Load Current
Up to 95% Efficiency
♦ Core Power
Adjustable from 1V to 5V
Internal Switches
Up to 1.5A Load Current
Up to 92% Efficiency
♦ 100% (max) Duty Cycle
♦ Up to 1.25MHz Switching Frequency
♦ Input Voltage Range from +2.7V to +28V
♦ 170µA Quiescent Current
♦ 5µA Shutdown Current
♦ Digital Soft-Start
♦ Independent Shutdown Inputs
MAX1775
Dual-Output Step-Down
DC-DC Converter for PDA/Palmtop Computers
________________________________________________________________ Maxim Integrated Products 1
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
SHDNM LXC
INC
GND
FBC
CS-
CS+
FBM
REF
TOP VIEW
MAX1775
16 QSOP
SHDNC
PGND
IN
NDRV
CVL
PDRV
CVH
Pin Configuration
19-1811; Rev 1; 8/01
EVALUA
TION KIT
AVAILA
BLE
Ordering Information
PART TEMP. RANGE PIN-PACKAGE
MAX1775EEE -40 °C to +85°C 16 QSOP
SHDNM
IN
IN 2.7V TO 5.5V (28V IN CASCADE)
CVH
CORE
1.8V
1.5A
MAIN
3.3V
OVER 2A SHDNC
ON
ON
OFF
OFF
NDRV
CS+
CS-
INC
FBM
LXC
FBC
CVL
REF
PGND
GND
PDRV
MAX1775
Typical Operating Circuit
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.