MAX8545 Datasheet, PDF (1/18 Pages) Maxim Integrated Products – Low-Cost, Wide Input Range, Step-Down Controllers with Foldback Current Limit

19-2795; Rev 0; 7/03
Low-Cost, Wide Input Range, Step-Down
Controllers with Foldback Current Limit
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.
Features
o 2.7V to 28V Input Range
o Foldback Short-Circuit Protection
o No Additional Bias Supply Needed
o 0.8V to 0.83 x V_IN Output
o Up to 95% Efficiency
o Low-Cost External Components
o No Current-Sense Resistor
o All N-Channel MOSFET Design
o Adaptive Gate Drivers Eliminate Shoot-Through
o Lossless Overcurrent and Short-Circuit
Protection
o 300kHz Switching Frequency
(MAX8545/MAX8546)
o 100kHz Switching Frequency (MAX8548)
o Pin-Compatible with the MAX1967
o Thermal Shutdown
PART
MAX8545EUB
MAX8546EUB
MAX8548EUB
Ordering Information
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
10 µMAX
10 µMAX
10 µMAX
Set-Top Boxes
Graphic Card and Video
Supplies
Desktops and Desknotes
PCI Express Power
Supplies
Telecom Power Supplies
Applications
Notebook Docking
Station Supplies
Cable Modems and
Routers
Networking Power
Supplies
PART
MAX8545
MAX8546
MAX8548
Selector Guide
SWITCHING
FREQUENCY
300kHz
300kHz
100kHz
CURRENT-LIMIT
THRESHOLD
-320mV
-165mV
-320mV
Typical Operating Circuit
INPUT
2.7V TO 28V
OFF
ON
V_CC VL
V_IN
BST
DH
MAX8545 ^LX
MAX8546
MAX8548 ^DL
COMP/
GND
EN
FB
OUTPUT
0.8V TO
0.9 x V_IN
UP TO 6A
OPTIONAL
Pin Configuration appears at end of data sheet.
________________________________________________________________ Maxim Integrated Products 1
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