MAX1765 Datasheet, PDF (1/19 Pages) Maxim Integrated Products – 800mA, Low-Noise, Step-Up DC-DC Converter with 500mA Linear Regulator

19-1805; Rev 0; 12/00
800mA, Low-Noise, Step-Up DC-DC Converter
with 500mA Linear Regulator
General Description
The MAX1765 is a high-efficiency, low-noise, step-up
DC-DC converter intended for use in battery-powered
wireless applications. This device operates at a high
1MHz fixed frequency while maintaining an exception-
ally low quiescent supply current (200µA). Its small
external components and tiny package make this
device an excellent choice for small hand-held applica-
tions that require the longest possible battery life.
The MAX1765 uses a synchronous-rectified pulse-
width-modulation (PWM) boost topology to generate
2.5V to 5.5V outputs from a wide range of input
sources, such as one to three alkaline or NiCd/NiMH
cells or a single lithium-ion (Li+) cell. Maxim's propri-
etary architecture significantly improves efficiency at
low load currents while automatically transitioning to
fixed-frequency PWM operation at medium to high load
currents to maintain excellent full-load efficiency.
Forced-PWM mode is available for applications that
require constant-frequency operation at all load cur-
rents, and the MAX1765 may also be synchronized to
an external clock to protect sensitive frequency bands
in communications equipment.
The MAX1765’s low-dropout (LDO) linear regulator and
DC-DC converter have separate shutdown control. The
linear regulator's 250mΩ pass device maintains excel-
lent dropout voltage at currents up to 500mA. The
MAX1765 also features analog soft-start and current-
limit functions to permit optimization of efficiency, exter-
nal component size, and output voltage ripple.
The MAX1765 comes in a 16-pin QSOP package and a
thermally enhanced 16-pin TSSOP-EP.
Typical Operating Circuit
ONL ONA
(0.7V TO 5.5V) 3.3µH
POUT
LX
INL
ONB
OUT
CLK/SEL
TRACK
FB
OUT = 3.3V
MAX1765
REF
ILIM
OUTL
GND FBL PGND
OUTL = 2.85V
(ADJ 1.25V
TO 5V)
____________________________Features
o High-Efficiency Step-Up Converter
Up to 93% Efficiency
Adjustable Output from +2.5V to +5.5V
Up to 800mA Output
PWM Synchronous-Rectified Topology
1MHz Operating Frequency (or Sync)
o LDO Linear Regulator
500mA LDO Linear Regulator
2.85V Linear Regulator Output or Adjustable
(1.25V to 5V)
Low 125mV Dropout at 500mA
o +0.7V to +5.5V Input Range
o 0.1µA Logic-Controlled Shutdown
o Adjustable Inductor Current Limit and Soft-Start
o Thermal Shutdown
o 1.5W, 16-Pin TSSOP-EP Package Available
PART
MAX1765EEE
MAX1765EUE
*Exposed pad
Ordering Information
TEMP. RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
16 QSOP
16 TSSOP-EP*
Wireless Handsets
PCS Phones
Palmtop Computers
Applications
Personal
Communicators
Hand-Held Instruments
Portable Audio Players
TOP VIEW
Pin Configuration
FBL 1
ISET 2
REF 3
GND 4
FB 5
OUT 6
ONA 7
CLK/SEL 8
MAX1765
16 ONL
15 TRACK
14 OUTL
13 INL
12 POUT
11 LX
10 PGND
9 ONB
QSOP/TSSOP-EP
________________________________________________________________ Maxim Integrated Products 1
For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.