MAX1774 Datasheet, PDF (1/21 Pages) Maxim Integrated Products – Dual, High-Efficiency, Step-Down Converter with Backup Battery Switchover

19-1810; Rev 1; 1/02
EVAALVUAAILTAIOBNLEKIT
Dual, High-Efficiency, Step-Down
Converter with Backup Battery Switchover
General Description
The MAX1774 is a complete power-supply solution for
PDAs and other hand-held devices. It integrates two
high-efficiency step-down converters, a boost converter
for backup battery regulation, and four voltage detec-
tors in a small 32-pin QFN or 28-pin QSOP package.
The MAX1774 accepts inputs from +2.7V to +28V and
provides an adjustable main output from 1.25V to 5.5V
at over 2A. The secondary core converter delivers an
adjustable voltage from 1V to 5V and can deliver up to
1.5A. Both the main and core regulators have separate
shutdown inputs.
When the AC adapter power is removed, an external P-
channel MOSFET switches input to the main battery.
When the main battery is low, the backup step-up con-
verter sustains the main output voltage. When the back-
up battery can no longer deliver the required load, the
system shuts down safely to prevent damage. Four on-
board voltage detectors monitor the status of the AC
adapter power, main battery, and backup battery.
The MAX1774 evaluation kit is available to help reduce
design time.
________________________Applications
Hand-Held Computers
PDAs
Internet Access Tablets
POS Terminals
Subnotebooks
Pin Configurations
TOP VIEW
GND
GND
MDRV 1
PGNDC 2
PGND 3
NDRV 4
CVL 5
IN 6
PDRV 7
CVH 8
MAX1774
24 ACO
23 INC
22 GND
21 FBC
20 CS-
19 CS+
18 FBM
17 N.C.
GND
GND
Features
o Dual, High-Efficiency, Synchronous-Rectified
Step-Down Converters
o Thin, Small (1mm High) QFN Package
o Step-Up Converter for Backup Battery
o Main Power
Adjustable from +1.25V to +5.5V
Over 2A Load Current
Up to 95% Efficiency
o Core Power
Adjustable from 1V to 5V
Internal Switches
Up to 1.5A Load Current
Up to 91% Efficiency
o Automatic Main Battery Switchover
o 100% (max) Duty Cycle
o Up to 1.25MHz Switching Frequency
o Input Voltage Range from +2.7V to +28V
o Four Low-Voltage Detectors
o 170µA Quiescent Current
o 8µA Shutdown Current
o Digital Soft-Start
o Independent Shutdown Inputs
Ordering Information
PART
MAX1774EEI
MAX1774EMJ
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
28 QSOP
32 7mm x 7mm QFN
Functional Diagram
AC
ADAPTER
MAIN
BATTERY
BACKUP
BATTERY
MAX1774
MAIN (+3.3V)
CORE (+1.8V)
AC OK
LOW MAIN BATTERY
DEAD MAIN BATTERY
32 7mm x 7mm QFN
Pin Configurations continued at end of data sheet.
________________________________________________________________ Maxim Integrated Products 1
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.