19-3623; Rev 0; 3/05
EVAALVUAAILTAIOBNLEKIT Integrated DDR Power-Supply Solution
for Desktops, Notebooks, and Graphic Cards
The MAX8632 integrates a synchronous-buck PWM con-
troller to generate VDDQ, a sourcing and sinking LDO lin-
ear regulator to generate VTT, and a 10mA reference
output buffer to generate VTTR. The buck controller drives
two external n-channel MOSFETs to generate output volt-
ages down to 0.7V from a 2V to 28V input with output cur-
rents up to 15A. The LDO can sink or source up to 1.5A
continuous and 3A peak current. Both the LDO output
and the 10mA reference buffer output can be made to
track the REFIN voltage. These features make the
MAX8632 ideally suited for DDR memory applications in
desktops, notebooks, and graphic cards.
The PWM controller in the MAX8632 utilizes Maxim’s
proprietary Quick-PWM™ architecture with programma-
ble switching frequencies of up to 600kHz. This control
scheme handles wide input/output voltage ratios with
ease and provides 100ns response to load transients
while maintaining high efficiency and a relatively con-
stant switching frequency. The MAX8632 offers fully pro-
grammable UVP/OVP and skip-mode options ideal in
portable applications. Skip mode allows for improved
efficiency at lighter loads.
The VTT and VTTR outputs track to within 1% of VREFIN / 2.
The high bandwidth of this LDO regulator allows excel-
lent transient response without the need for bulk capac-
itors, thus reducing cost and size.
The buck controller and LDO regulators are provided with
independent current limits. Adjustable lossless foldback
current limit for the buck regulator is achieved by monitor-
ing the drain-to-source voltage drop of the low-side
MOSFET. Additionally, overvoltage and undervoltage pro-
tection mechanisms are built in. Once the overcurrent
condition is removed, the regulator is allowed to enter
soft-start again. This helps minimize power dissipation
during a short-circuit condition. The MAX8632 allows flex-
ible sequencing and standby power management using
the SHDN and STBY inputs, which support all DDR
The MAX8632 is available in a small 5mm × 5mm, 28-
pin thin QFN package.
DDR I and DDR II Memory Power Supplies
Notebooks and Desknotes
♦ Quick-PWM with 100ns Load-Step Response
♦ Up to 95% Efficiency
♦ 2V to 28V Input Voltage Range
♦ 1.8V/2.5V Fixed or 0.7V to 5.5V Adjustable Output
♦ Up to 600kHz Selectable Switching Frequency
♦ Programmable Current Limit with Foldback
♦ 1.7ms Digital Soft-Start
♦ Independent Shutdown and Standby Controls
♦ Overvoltage-/Undervoltage-Protection Option
♦ Power-Good Window Comparator
♦ Fully Integrated VTT and VTTR Capability
♦ VTT Has ±3A Sourcing/Sinking Capability
♦ Only 20µF Ceramic Capacitance Required for VTT
♦ VTT and VTTR Outputs Track VREFIN / 2
♦ All-Ceramic Output-Capacitor Designs
♦ 1.0V to 2.8V Input Voltage Range
♦ Power-Good Window Comparator
TEMP RANGE PIN-PACKAGE
-40°C to +85°C 28 Thin QFN 5mm × 5mm
+Denotes lead-free packaging.
21 20 19 18 17 16 15
1 23 4 56 7
5mm x 5mm THIN QFN
Typical Operating Circuit appears 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.