Rainbow Electronics MAX8548 - Manual

General Description
The MAX8545/MAX8546/MAX8548 are voltage-mode
pulse-width-modulated (PWM), step-down DC-DC con-
trollers ideal for a variety of cost-sensitive applications.
They drive low-cost N-channel MOSFETs for both the
high-side switch and synchronous rectifier, and require
no external current-sense resistor. These devices can
supply output voltages as low as 0.8V.
The MAX8545/MAX8546/MAX8548 have a wide 2.7V to
28V input range, and do not need any additional bias
voltage. The output voltage can be precisely regulated
from 0.8V to 0.83 x V
IN . These devices can provide effi-
ciency up to 95%. Lossless short-circuit and current-limit
protection is provided by monitoring the R
DS(ON) of the
low-side MOSFET. The MAX8545 and MAX8548 have a
current-limit threshold of 320mV, while the MAX8546 has
a current-limit threshold of 165mV. All devices feature
foldback-current capability to minimize power dissipation
under short-circuit condition. Pulling the COMP/EN pin
low with an open-collector or low-capacitance, open-
drain device can shut down all devices.
The MAX8545/MAX8546 operate at 300kHz and the
MAX8548 operates at 100kHz. The MAX8545/
MAX8546/MAX8548 are compatible with low-cost alu-
minum electrolytic capacitors. Input undervoltage lock-
out prevents proper operation under power-sag
operations to prevent external MOSFETs from overheat-
ing. Internal soft-start is included to reduce inrush cur-
rent. These devices are offered in space-saving 10-pin
µMAX packages.
Applications
Features
♦ 2.7V to 28V Input Range
♦ Foldback Short-Circuit Protection
♦ No Additional Bias Supply Needed
♦ 0.8V to 0.83 x V
IN Output
♦ Up to 95% Efficiency
♦ Low-Cost External Components
♦ No Current-Sense Resistor
♦ All N-Channel MOSFET Design
♦ Adaptive Gate Drivers Eliminate Shoot-Through
♦ Lossless Overcurrent and Short-Circuit
Protection
♦ 300kHz Switching Frequency
(MAX8545/MAX8546)
♦ 100kHz Switching Frequency (MAX8548)
♦ Pin-Compatible with the MAX1967
♦ Thermal Shutdown
MAX8545/MAX8546/MAX8548
Low-Cost, Wide Input Range, Step-Down
Controllers with Foldback Current Limit
________________________________________________________________ Maxim Integrated Products 1
MAX8545
MAX8546
MAX8548
ON
OFF
OPTIONAL
BST V IN
COMP/
EN
VL V CC
DH
LX
DL
GND
FB
INPUT
2.7V TO 28V
OUTPUT
0.8V TO
0.9 x V IN
UP TO 6A
Typical Operating Circuit
Ordering Information
Pin Configuration appears at end of data sheet.
19-2795; Rev 0; 7/03
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.
PART TEMP RANGE PIN-PACKAGE
MAX8545EUB -40 °C to +85°C 10 µMAX
MAX8546EUB -40 °C to +85°C 10 µMAX
MAX8548EUB -40 °C to +85°C 10 µMAX
Selector Guide
PART
SWITCHING
FREQUENCY
CURRENT-LIMIT
THRESHOLD
MAX8545 300kHz -320mV
MAX8546 300kHz -165mV
MAX8548 100kHz -320mV
Set-Top Boxes
Graphic Card and Video
Supplies
Desktops and Desknotes
PCI Express Power
Supplies
Telecom Power Supplies
Notebook Docking
Station Supplies
Cable Modems and
Routers
Networking Power
Supplies