19-4505; Rev 4; 7/05
5V/3.3V/3V/Adjustable, High-Efficiency,
Low IQ, Step-Down DC-DC Converters
____________________________Features
The MAX639/MAX640/MAX653 step-down switching
regulators provide high efficiency over a wide range of
load currents, delivering up to 225mA. A current-limiting
pulse-frequency-modulated (PFM) control scheme gives
the devices the benefits of pulse-width-modulated
(PWM) converters (high efficiency at heavy loads), while
using only 10µA of supply current (vs. 2mA to 10mA for
PWM converters). The result is high efficiency over a
wide range of loads.
♦ High Efficiency for a Wide Range of Load Currents
The MAX639/MAX640/MAX653 input range is 4V to
11.5V, and the devices provide lower preset output voltages of 5V, 3.3V, and 3V, respectively. Or, the output
can be user-adjusted to any voltage from 1.3V to the
input voltage.
♦ Low-Battery Detection Comparator
The MAX639/MAX640/MAX653 have an internal 1A power
MOSFET switch, making them ideal for minimum-component, low- and medium-power applications. For increased
output drive capability, use the MAX649/MAX651/MAX652
step-down controllers, which drive an external P-channel
FET to deliver up to 5W.
________________________Applications
9V Battery to 5V, 3.3V, or 3V Conversion
High-Efficiency Linear Regulator Replacement
Portable Instruments and Handy-Terminals
♦ 10µA Quiescent Current
♦ Output Currents Up to 225mA
♦ Preset or Adjustable Output Voltage:
5.0V (MAX639)
3.3V (MAX640)
3.0V (MAX653)
♦ Current-Limiting PFM Control Scheme
______________Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX639CPA
0°C to +70°C
8 Plastic DIP
MAX639CSA
MAX639C/D
MAX639EPA
MAX639ESA
MAX639MJA
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
8 SO
Dice*
8 Plastic DIP
8 SO
8 CERDIP
Ordering Information continued on last page.
*Contact factory for dice specifications.
5V-to-3.3V Converters
__________Typical Operating Circuit
__________________Pin Configuration
TOP VIEW
INPUT
5.5V TO 11.5V
V+
OUTPUT
5V
225mA
LX
VOUT
LBO
LOW-BATTERY
DETECTOR
INPUT
SHDN
VOUT
LBI
LBO
LOW-BATTERY
DETECTOR
OUTPUT
2
LBI
MAX639
ON/OFF
8 SHDN
1
3
GND
MAX639
MAX640
MAX653
4
7
VFB
6
V+
5 LX
DIP/SO
VFB
GND
________________________________________________________________ Maxim Integrated Products
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.
1
MAX639/MAX640/MAX653
_______________General Description
