MAX8550A Datasheet, PDF (1/29 Pages) Maxim Integrated Products – Intergrated DDR Power-Solution for Desktops, Notebooks, and Graphi Bill

19-3173; Rev 0; 5/04
EVAALVUAAILTAIOBNLEKIT
Integrated DDR Power-Supply Solution for
Desktops, Notebooks, and Graphic Cards
General Description
The MAX8550A integrates a synchronous-buck PWM
controller to generate V_DDQ, a sourcing and sinking LDO
linear regulator to generate V_TT, and a 10mA reference
output buffer to generate V_TTR. 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
MAX8550A ideally suited for DDR memory applications in
desktops, notebooks, and graphic cards.
The PWM controller in the MAX8550A 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 MAX8550A offers fully
programmable 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 V_REFIN / 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 MAX8550A allows
flexible sequencing and standby power management
using the SHDN and STBY inputs, which support all
DDRs’ operating states.
The MAX8550A is available in a small 5mm × 5mm, 28-
pin thin QFN package.
Applications
DDR I and DDR II Memory Power Supplies
Desktop Computers
Notebooks and Desknotes
Graphic Cards
Game Consoles
RAID
Networking
Buck Controller
Features
♦ 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
Capability
♦ 1.7ms Digital Soft-Start
♦ Independent Shutdown and Standby Controls
♦ Overvoltage/Undervoltage-Protection Option
♦ Power-Good Window Comparator
LDO Section
♦ Fully Integrated VTT and VTTR Capability
♦ VTT Has ±3A Sourcing/Sinking Capability
♦ VTT and VTTR Outputs Track V_REFIN / 2
♦ All-Ceramic Output-Capacitor Designs
♦ 1.0V to 2.8V Input Voltage Range
♦ Power-Good Window Comparator
Ordering Information
PART
MAX8550AETI
TEMP RANGE PIN-PACKAGE
-40°C to +85°C 28 TQFN 5mm × 5mm
TOP VIEW
Pin Configuration
TON 1
OVP/UVP 2
REF ³
ILIM 4
POK1 5
POK2 6
STBY 7
MAX8550A
21 DL
20 BST
19 LX
18 DH
17 V_IN
16 OUT
15 FB
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.