MAX1626 Datasheet, PDF (1/16 Pages) Maxim Integrated Products – 5V/3.3V or Adjustable, 100% Duty-Cycle, High-Efficiency, Step-Down DC-DC Controllers

19-1075; Rev 0; 6/96
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5V/3.3V or Adjustable, 100% Duty-Cycle,
High-Efficiency, Step-Down DC-DC Controllers
_______________General Description
The MAX1626/MAX1627 step-down DC-DC switching
controllers provide high efficiency over loads ranging
from 1mA to more than 2A. A unique current-limited,
pulse-frequency-modulated (PFM) control scheme
operates with up to a 100% duty cycle, resulting in very
low dropout voltages. This control scheme eliminates
minimum load requirements and reduces the supply
current under light loads to 90µA (versus 2mA to 10mA
for common pulse-width modulation controllers).
These step-down controllers drive an external P-chan-
nel MOSFET, allowing design flexibility for applications
to 12W or higher. Soft-start reduces current surges dur-
ing start-up. A high switching frequency (up to 300kHz)
and operation in continuous-conduction mode allow the
use of tiny surface-mount inductors. Output capacitor
requirements are also reduced, minimizing PC board
area and system costs.
The output voltage is preset at 5V or 3.3V for the
MAX1626 and adjustable for the MAX1627. Input volt-
ages can be up to 16.5V. The MAX1626/MAX1627 are
functional upgrades for the MAX1649/MAX1651.
____________________________Features
o Low Dropout Voltage
o 100% Maximum Duty Cycle
o Soft-Start Limits Start-Up Current
o Efficiency >90% (3mA to 2A Loads)
o Output Power >12.5W
o 90µA Max Quiescent Current
o 1µA Max Shutdown Current
o Up to 300kHz Switching Frequency
o 16.5V Max Input Voltage
o Output Voltage: 5V/3.3V (MAX1626)
Adjustable (MAX1627)
o Current-Limited Control Scheme
______________Ordering Information
________________________Applications
PCMCIA Power Supplies
Personal Digital Assistants
Hand-Held Computers
Portable Terminals
Low-Cost Notebook Computer Supplies
5V to 3.3V Green PC Applications
High-Efficiency Step-Down Regulation
Minimum-Component DC-DC Converters
Battery-Powered Applications
__________________Pin Configuration
TOP VIEW
OUT ₁
3/5 (FB) 2
SHDN 3
REF 4
MAX1626
MAX1627
8 GND
7 EXT
6 CS
5 V+
SO
( ) ARE FOR MAX1627
PART
TEMP. RANGE
MAX1626C/D
0°C to +70°C
MAX1626ESA
-40°C to +85°C
MAX1627C/D
MAX1627ESA
0°C to +70°C
-40°C to +85°C
* Dice are tested at TA = +25°C.
PIN-PACKAGE
Dice*
8 SO
Dice*
8 SO
__________Typical Operating Circuit
INPUT
3.3V to 16.5V
V+
ON/OFF
MAX1626
SHDN
CS
EXT
P
3/5
REF
OUT
GND
OUTPUT
3.3V
________________________________________________________________ Maxim Integrated Products 1
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