MAX649 Datasheet, PDF (1/16 Pages) Maxim Integrated Products – 5V/3.3V/3V or Adjustable, High-Efficiency,

19-0225; Rev 3; 9/97
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5V/3.3V/3V or Adjustable, High-Efficiency,
Low IQ, Step-Down DC-DC Controllers
_______________General Description
The MAX649/MAX651/MAX652 BiCMOS, step-down DC-
DC switching controllers provide high efficiency over
three decades of load current. A unique, current-limited
pulse-frequency-modulated (PFM) control scheme gives
these devices the benefits of pulse-width-modulation
(PWM) converters (high efficiency at heavy loads), while
using only 100µA of supply current (vs. 2mA to 10mA for
PWM converters). The result is high efficiency over loads
ranging from 10mA to more than 2.5A.
These devices use miniature external components.
Their high switching frequency (up to 300kHz) allows
for less than 9mm diameter surface-mount inductors.
The MAX649/MAX651/MAX652 have dropout voltages
less than 1V and accept input voltages up to 16.5V.
Output voltages are preset at 5V (MAX649), 3.3V
(MAX651), and 3V (MAX652). These controllers can
also be adjusted to any voltage from 1.5V to the input
voltage by using two resistors.
These step-down controllers drive external P-channel
MOSFETs at loads greater than 10W. If less power is
required, use the MAX639/MAX640/MAX653 step-down
converters with on-chip FETs, which allow up to a
225mA load current.
________________________Applications
5V-to-3.3V Green PC Applications
High-Efficiency Step-Down Regulation
Minimum-Component DC-DC Converters
Battery-Powered Applications
____________________________Features
o More than 90% Efficiency (10mA to 1.5A Loads)
o More than 12.5W Output Power
o 100µA Max Quiescent Supply Current
o 5µA Max Shutdown Supply Current
o Less than 1.0V Dropout Voltage
o 16.5V Max Input Voltage
o 5V (MAX649), 3.3V (MAX651), 3V (MAX652),
or Adjustable Output Voltage
o Current-Limited Control Scheme
o Up to 300kHz Switching Frequency
______________Ordering Information
PART
TEMP. RANGE
PIN-PACKAGE
MAX649CPA
0°C to +70°C
8 Plastic DIP
MAX649CSA
0°C to +70°C
8 SO
MAX649C/D
0°C to +70°C
Dice*
MAX649EPA
-40°C to +85°C
8 Plastic DIP
MAX649ESA
-40°C to +85°C
8 SO
MAX649MJA
-55°C to +125°C 8 CERDIP**
Ordering Information continued at end of data sheet.
* Dice are tested at T_A = +25°C.
**Contact factory for availability and processing to MIL-STD-883.
__________Typical Operating Circuit __________________Pin Configuration
INPUT
4V TO 16.5V
TOP VIEW
V+
ON/OFF
MAX651
SHDN
CS
EXT
P
REF
OUT
FB GND
OUTPUT
3.3V
OUT ₁
FB 2
SHDN 3
REF 4
MAX649
MAX651
MAX652
8 GND
7 EXT
6 CS
5 V+
DIP/SO
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