19-1198; Rev 0; 4/97
1- to 3-Cell, High-Current, Low-Noise,
Step-Up DC-DC Converters with Linear Regulator
_______________General Description
The MAX1705/MAX1706 are high-efficiency, low-noise,
step-up DC-DC converters with an auxiliary linear-
regulator output. These devices are intended for use in
battery-powered wireless applications. They use a syn-
chronous rectifier pulse-width-modulation (PWM) boost
topology to generate 2.5V to 5.5V outputs from battery
inputs, such as 1 to 3 NiCd/NiMH cells or 1 Li-Ion cell.
The MAX1705 has an internal 1A N-channel MOSFET
switch. The MAX1706 has a 0.5A switch. Both devices
also have a built-in low-dropout linear regulator that
delivers up to 200mA.
With an internal synchronous rectifier, the MAX1705/
MAX1706 deliver 5% better efficiency than similar non-
synchronous converters. They also feature a pulse-
frequency-modulation (PFM) standby mode to improve
efficiency at light loads, and a 1µA shutdown mode. An
efficiency-enhancing track mode reduces the step-up
DC-DC converter output to 300mV above the linear-reg-
ulator output.
Both devices come in a 16-pin QSOP package, which
occupies the same space as an 8-pin SO. Other features
include two shutdown-control inputs for push-on/push-off
control, and an uncommitted comparator for use as a volt-
age monitor.
L
MANUA
ION KIT
AT
EVALU
BLE
AVAILA
____________________________Features
o
Up to 96% Efficiency
o
1.1V
IN
Guaranteed Start-Up
o
Up to 850mA Output (MAX1705)
o
Step-Up Output (2.5V to 5.5V adjustable)
o
Linear Regulator (1.25V to 5.0V adjustable)
o
PWM/PFM Synchronous-Rectified Topology
o
300kHz PWM Mode or Synchronizable
o
1µA Shutdown Mode
o
Voltage Monitor
o
Pushbutton On/Off Control
MAX1705/MAX1706
______________Ordering Information
PART
MAX1705C/D
TEMP. RANGE
0°C to +70°C
PIN-PACKAGE
Dice*
16 QSOP
-40°C to +85°C
MAX1705EEE
Dice*
MAX1706C/D
0°C to +70°C
16 QSOP
MAX1706EEE
-40°C to +85°C
*Dice
are tested at T
A
= +25°C, DC parameters only.
________________________Applications
Digital Cordless Phones
Personal Communicators
Palmtop Computers
Hand-Held Instruments
PCS Phones
Wireless Handsets
Two-Way Pagers
__________Typical Operating Circuit
INPUT 0.7V TO 5.5V
__________________Pin Configuration
LOW-BATTERY
DETECTION
LX
LBP
POUT
OUT
STEP-UP OUTPUT
TOP VIEW
LBP 1
LBN 2
REF 3
TRACK 4
GND 5
OUT 6
FB 7
FBLDO 8
16 POUT
LBO
15 ONA
14 ONB
MAX1705
MAX1706
FB
ON/OFF CONTROL
HIGH
EFFICIENCY
LOW
NOISE
ONA
ONB
CLK/SEL
TRACK
LBN
REF
LDO
FBLDO
GND PGND
LINEAR
REGULATOR
OUTPUT
MAX1705
MAX1706
13 LX
12 PGND
11 CLK/SEL
10 LBO
9
LDO
QSOP
________________________________________________________________
Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
