19-1454; Rev 0; 4/99
Low-Noise, 14V Input, 1A, PWM
The MAX1684/MAX1685 are high-efficiency, internal-
switch, PWM step-down switching regulators intended to
power cellular phones, communicating PDAs, and
handy-terminals. These devices deliver a guaranteed 1A
output current from two Li-Ion 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 bat-
tery is removed. The output voltage is preset to 3.3V or
can be externally adjusted from 1.25V to VIN.
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
mode, normal mode, low-power mode, and shutdown
mode. The fixed-frequency PWM mode of operation
offers excellent noise characteristics. 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 current draw.
The MAX1684 runs at 300kHz for applications that
require highest efficiency. The MAX1685 runs at
600kHz to allow use of smaller external components.
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), see the MAX1692 data sheet.
2-Way Radios and Walkie-Talkies
PDAs and Handy-Terminals
Pin Configuration appears at end of data sheet.
o Up to 96% Efficiency
o 1A Guaranteed Output Current
o 100% Duty Cycle in Dropout
o 2.7V to 14V Input Range (15V absolute max)
o ±1% Accurate Reference Output
o 0.24Ω P-Channel On-Resistance
o Synchronizable Switching Frequency
o Fixed-Frequency PWM Operation
o 150µA Normal Mode Quiescent Current
o 25µA Low-Power Mode Quiescent Current
o 2µA Shutdown Current
o Dual Mode™ Fixed 3.3V (±1%) Output or
Adjustable Output (1.25V to VIN)
o Small 16-QSOP Package
o Auxiliary Output (CVL): 3V/5mA
-40°C to +85°C
-40°C to +85°C
Typical Operating Circuit
2.7V TO 14V
FB CC REF
3.3V AT 1A
Dual Mode is a trademark of Maxim Integrated Products.
________________________________________________________________ Maxim Integrated Products 1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
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