19-3017; Rev 0; 10/03
4.5V to 28V Input, Synchronous PWM Buck Controllers
for DDR Termination and Point-of-Load Applications
General Description
Features
The MAX8553 is a 4.5V to 28V input-voltage, synchro-
nous step-down controller that provides a complete
power-management solution for DDR memory. The
ꢀ Up to 25A Output-Current Capability
ꢀ Quick-PWM Control for Fast Loop Response
ꢀ Up to 95% Efficiency
MAX8553 generates 1/2 V
voltage for VTT and
REFIN
VTTR. The VTT and VTTR tracking voltages are main-
tained within 1% of 1/2 V . The MAX8554 is a 4.5V to
ꢀ 4.5V to 28V Input Voltage Range
REFIN
28V input voltage, nontracking step-down controller with
a low 0.6V feedback threshold voltage. The MAX8553/
MAX8554 use Maxim’s proprietary Quick-PWM™ archi-
tecture for fast transient response and operate with
selectable pseudo-fixed frequencies. Both controllers
can operate without an external bias supply.
ꢀ No External Bias Supply Required
ꢀ 0 to 3.6V Input REFIN Range (MAX8553)
ꢀ Automatically Sets VTT and VTTR to within 1%
of 1/2 V
- (MAX8553)
REFIN
ꢀ Low 0.6V Feedback Threshold (MAX8554)
The controllers operate in synchronous-rectification mode
to ensure balanced current sourcing and sinking capabili-
ty of up to 25A. The MAX8553/MAX8554 also provide up
to 95% efficiency, making them ideal for server and point-
of-load applications. Additionally, a low 5µA shutdown
current allows for longer battery life in notebook applica-
tions. Lossless current monitoring is achieved by monitor-
ing the low-side MOSFET’s drain-to-source voltage. The
MAX8553/MAX8554 have an adjustable foldback current
limit to withstand a continuous output overload and short
circuit. Digital soft-start provides control of inrush current
during power-up. Overvoltage protection shuts the con-
verter down and discharges the output capacitor. The
MAX8553/MAX8554 come in space-saving 16-pin QSOP
packages.
ꢀ 200kHz/300kHz/400kHz/550kHz Selectable
Switching Frequencies
ꢀ Adjustable Foldback Current Limit
ꢀ Overvoltage Protection
ꢀ Digital Soft-Start
Typical Operating Circuit
VIN
+5V
DH
EN/HSD
Applications
Wide-Input Power Supplies
MAX8553
POK
VL
BST
LX
POK
REFIN
V+
Servers and Storage Applications
ASIC and CPU Core Voltages
REFIN
VOUT
V+
Notebook and LCD-PC Power Supplies
DDR I and DDR II Memory Power Supplies
AGTL Bus Termination Supplies
DL
REF
PGND
VTT
ILIM
FSEL
GND
Ordering Information
PART
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
16 QSOP
VTTR
MAX8553EEE
MAX8554EEE
VTTR
16 QSOP
Pin Configurations appear at end of data sheet.
Quick-PWM is a trademark of Maxim Integrated Products, Inc.
________________________________________________________________ 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.