MAX1945R Datasheet, PDF (1/19 Pages) Maxim Integrated Products – 1MHz, 1% Accurate, 6A Internal Switch Step-Down Regulators

19-2640; Rev 1; 7/04
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1MHz, 1% Accurate, 6A Internal Switch
Step-Down Regulators
General Description
The MAX1945R/MAX1945S high-efficiency pulse-width
modulation (PWM) switching regulators deliver up to 6A
of output current. The devices operate from an input
supply range of 2.6V to 5.5V and provide selectable
output voltages of 1.8V, 2.5V, and adjustable output
voltages from 0.8V to 85% of the supply voltage. With
V_CC at 3.3V/5V, the input voltage can be as low as
2.25V. The MAX1945R/MAX1945S are ideal for on-
board post-regulation applications. Total output voltage
error is less than ±1% over load, line, and temperature.
The MAX1945R/MAX1945S operate at a selectable
fixed frequency (500kHz or 1MHz) or can be synchro-
nized to an external clock (400kHz to 1.2MHz). The
high operating frequency minimizes the size of external
components. The high bandwidth of the internal error
amplifier provides excellent transient response. The
MAX1945R/MAX1945S have internal dual N-channel
MOSFETs to lower heat dissipation at heavy loads. Two
MAX1945R/MAX1945Ss can operate 180 degrees out-
of-phase of each other to minimize input capacitance.
The devices provide output voltage margining for
board-level testing. The MAX1945R provides a ±4%
voltage margining. The MAX1945S provides a ±9%
voltage margining.
The MAX1945R/MAX1945S are available in 28-pin
TSSOP-EP packages and are specified over the -40°C
to +85°C industrial temperature range. An evaluation kit
is available to speed designs.
Applications
Low-Voltage, High-Density Distributed Power
Supplies
ASIC, CPU, and DSP Core Voltages
RAM Power Supply
Base Station, Telecom, and Networking
Equipment Power Supplies
Server and Notebook Power Supplies
Pin Configuration appears at end of data sheet.
Features
♦ 6A PWM Step-Down Regulator with 95%
Efficiency
♦ 1MHz/500kHz Switching for Small External
Components
♦ 0.76in² Complete 6A Regulator Footprint
♦ External Components’ Height <3mm
♦ ±1% Output Accuracy over Load, Line, and
Temperature
♦ Operate from 2.6V to 5.5V Supply
♦ Operate from 2.5V Input with V_CC at 3.3V/5V
♦ Preset Output Voltage of 1.8V or 2.5V
♦ Adjustable Output from 0.8V to 85% of Input
♦ Voltage Margining: ±4% (MAX1945R) or ±9%
(MAX1945S)
♦ Synchronize to External Clock
♦ SYNCOUT Provides 180-Degree Out-of-Phase
Clock Output
♦ All-Ceramic or Electrolytic Capacitor Designs
Ordering Information
PART
MAX1945REUI
MAX1945SEUI
*EP = Exposed pad.
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
28 TSSOP-EP*
28 TSSOP-EP*
Typical Operating Circuit
INPUT
2.6V TO 5.5V
VOLTAGE
MARGINING
ON/OFF
SYNCHRONIZATION
CLOCK
BST
IN
LX
V_DD
V_{CC MAX1945R}
MAX1945S
CTL1
PGND
CTL2
SYNC
COMP
FB
SYNCOUT
FBSEL
REF
GND
OUTPUT
0.8V TO
0.85 x V_IN,
6A
180° OUT-OF-PHASE
________________________________________________________________ Maxim Integrated Products 1
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.