MAX1705 Datasheet, PDF (1/20 Pages) Maxim Integrated Products – 1- to 3-Cell, High-Current, Low-Noise, Step-Up DC-DC Converters with Linear Regulator

19-1198; Rev 0; 4/97
EVALUAATVIOANILKAIBTLMEANUAL _{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.
________________________Applications
Digital Cordless Phones
Personal Communicators
Palmtop Computers
Hand-Held Instruments
PCS Phones
Wireless Handsets
Two-Way Pagers
__________________Pin Configuration
TOP VIEW
LBP 1
LBN 2
REF 3
TRACK 4
GND 5
OUT 6
FB 7
FBLDO 8
MAX1705
MAX1706
QSOP
16 POUT
15 ONA
14 ONB
13 LX
12 PGND
11 CLK/SEL
10 LBO
9 LDO
____________________________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
______________Ordering Information
PART
TEMP. RANGE
PIN-PACKAGE
MAX1705C/D
0°C to +70°C
Dice*
MAX1705EEE
-40°C to +85°C
16 QSOP
MAX1706C/D
0°C to +70°C
Dice*
MAX1706EEE
-40°C to +85°C
16 QSOP
*Dice are tested at T_A = +25°C, DC parameters only.
__________Typical Operating Circuit
INPUT 0.7V TO 5.5V
LOW-BATTERY
DETECTION
ON/OFF CONTROL
HIGH
EFFICIENCY
LOW
NOISE
LX
LBP
POUT
OUT
MAX1705 FB
LBO _MAX1706
ONA
ONB
CLK/SEL
TRACK
LBN
LDO
FBLDO
REF
GND PGND
STEP-UP OUTPUT
LINEAR
REGULATOR
OUTPUT
________________________________________________________________ Maxim Integrated Products 1
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