Rainbow Electronics MAX1685 - Manual

General Description
The MAX1684/MAX1685 are high-efficiency, internal-
switch, pulse-width modulation (PWM) step-down switch-
ing regulators intended to power cellular phones,
communicating PDAs, and handy-terminals. These
devices deliver a guaranteed 1A output current from two
lithium-ion (Li+) batteries. Their wide-input voltage range
of 2.7V to 14V gives design flexibility and allows batteries
to charge from a wall cube, since the ICs operate at the
higher voltages that occur when the battery is removed.
The output voltage is preset to 3.3V or can be externally
adjusted from 1.25V to V
IN .
The low on-resistance power switch and built-in synchro-
nous rectifier provide high efficiencies of up to 96%.
There are four modes of operation: fixed-frequency, nor-
mal, low-power, and shutdown. The fixed-frequency
PWM mode of operation offers excellent noise character-
istics. The normal mode maintains high efficiency at all
loads. The low-power mode is used to conserve power in
standby or when full load is not required. The shutdown
mode is used to power down the device for minimal cur-
rent draw.
The MAX1684 runs at 300kHz for applications that
require highest efficiency. The MAX1685 runs at
600kHz to allow the use of smaller external compo-
nents. These devices can also be synchronized to an
external clock. Other features include a 100% duty
cycle for low-dropout applications, an auxiliary 3V/5mA
output, and a 1% accurate reference.
Both devices are available in a space-saving 16-QSOP
package. An evaluation kit is also available to help
speed designs. For a similar device in a 10-pin µMAX
package with lower input voltage requirements (5.5V
max), refer to the MAX1692 data sheet.
Applications
Cellular Phones
Two-Way Radios and Walkie-Talkies
Computer Peripherals
Personal Communicators
PDAs and Handy-Terminals
Features
♦ Up to 96% Efficiency
♦ 1A Guaranteed Output Current
♦ 100% Duty Cycle in Dropout
♦ 2.7V to 14V Input Range (15V Absolute Max)
♦ ±1% Accurate Reference Output
♦ 0.24Ω P-Channel On-Resistance
♦ Synchronizable Switching Frequency
♦ Fixed-Frequency PWM Operation
300kHz (MAX1684)
600kHz (MAX1685)
♦ 150µA Normal-Mode Quiescent Current
♦ 25µA Low-Power Mode Quiescent Current
♦ 2µA Shutdown Current
♦ Dual Mode™ Fixed 3.3V (±1%) Output or
Adjustable Output (1.25V to V IN )
♦ Small 16-QSOP Package
♦ Auxiliary Output (CVL): 3V/5mA
MAX1684/MAX1685
Low-Noise, 14V Input, 1A, PWM
Step-Down Converters
MAX1684
MAX1685
LX IN
AIN
GND
OUTPUT
3.3V AT 1A INPUT
2.7V TO 14V
BOOT
SHDN
CVH
CVL
STBY
SYNC/PWM
FB CC REF
+ +
19-1454; Rev 2; 7/01
PART
MAX1684EEE
MAX1685EEE -40°C to +85°C
-40°C to +85°C
TEMP RANGE PIN-PACKAGE
16 QSOP
16 QSOP
EVALUATION KIT
AVAILABLE
Typical Operating Circuit
Ordering Information
Pin Configuration appears at end of data sheet.
Dual Mode is a trademark of Maxim Integrated Products, Inc.
________________________________________________________________ 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.