Rainbow Electronics MAX1765 - Manual

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 250m
Ω 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.
____________________________Features
♦ 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)
♦ LDO Linear Regulator
500mA LDO Linear Regulator
2.85V Linear Regulator Output or Adjustable
(1.25V to 5V)
Low 125mV Dropout at 500mA
♦ +0.7V to +5.5V Input Range
♦ 0.1µA Logic-Controlled Shutdown
♦ Adjustable Inductor Current Limit and Soft-Start
♦ Thermal Shutdown
♦ 1.5W, 16-Pin TSSOP-EP Package Available
MAX1765
800mA, Low-Noise, Step-Up DC-DC Converter
with 500mA Linear Regulator
________________________________________________________________ Maxim Integrated Products 1
19-1805; Rev 0; 12/00
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.
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FBL ONL
TRACK
INL
POUT
LX
PGND
OUTL
TOP VIEW
MAX1765
QSOP/TSSOP-EP
ONB
ISET
REF
OUT
GND
FB
ONA
CLK/SEL
Pin Configuration
Wireless Handsets
PCS Phones
Palmtop Computers
Personal
Communicators
Hand-Held Instruments
Portable Audio Players
Applications
FBL
REF
ILIM
ONL ONA
(0.7V TO 5.5V) 3.3 µH
OUTL = 2.85V
(ADJ 1.25V
TO 5V)
OUT = 3.3V
OUT
OUTL
POUT
FB
GND PGND
TRACK
LX
CLK/SEL
ONB
INL
MAX1765
Typical Operating Circuit
Ordering Information
*Exposed pad
PART TEMP. RANGE PIN-PACKAGE
MAX1765EEE -40 °C to +85°C 16 QSOP
MAX1765EUE -40 °C to +85°C 16 TSSOP-EP*