1
®
ISL6531
Dual 5V Synchronous Buck Pulse-Width
Modulator (PWM) Controller for DDRAM
Memory V
DDQ
and V
TT
Termination
The ISL6531 provides complete control and protection for
dual DC-DC converters optimized for high-performance
DDRAM memory applications. It is designed to drive low
cost N-channel MOSFETs in synchronous-rectified buck
topology to efficiently generate 2.5V V
DDQ
for powering
DDRAM memory, V
REF
for DDRAM differential signalling,
and V
TT
for signal termination. The ISL6531 integrates all of
the control, output adjustment, monitoring and protection
functions into a single package.
The V
DDQ
output of the converter is maintained at 2.5V
through an integrated precision voltage reference. The V
REF
output is precisely regulated to 1/2 the memory power
supply, with a maximum tolerance of ±1% over temperature
and line voltage variations. V
TT
accurately tracks V
REF
.
During V2_SD sleep mode, the V
TT
output is maintained by
a low power window regulator.
The ISL6531 provides simple, single feedback loop, voltage-
mode control with fast transient response for the V
DDQ
regulator. The V
TT
regulator features internal compensation
that eases the design. It includes two phase-locked 300kHz
triangle-wave oscillators which are displaced 90
o
to minimize
interference between the two PWM regulators. The
regulators feature error amplifiers with a 15MHz gain-
bandwidth product and 6V/µs slew rate which enables high
converter bandwidth for fast transient performance. The
resulting PWM duty ratio ranges from 0% to 100%.
The ISL6531 protects against overcurrent conditions by
inhibiting PWM operation. The ISL6531 monitors the current
in the V
DDQ
regulator by using the r
DS(ON)
of the upper
MOSFET which eliminates the need for a current sensing
resistor.
Ordering Information
Features
• Provides V
DDQ
, V
REF
, and V
TT
voltages for one- and two-
channel DDRAM memory systems
• Excellent voltage regulation
-V
DDQ
= 2.5V ±2% over full operating range
-V
REF
= ±1% over full operating range
-V
TT
= V
REF
± 30mV
• Supports ‘S3’ sleep mode
-V
TT
is held at via a low power window
regulator to minimize wake-up time
• Fast transient response
- Full 0% to 100% duty ratio
• Operates from +5V Input
•V
TT
regulator internally compensated
• Overcurrent fault monitor on VDD
- Does not require extra current sensing element
- Uses MOSFET’s r
DS(ON)
• Drives inexpensive N-Channel MOSFETs
• Small converter size
- 300kHz fixed frequency oscillator
• 24 Lead, SOIC or 32 Lead, 5mm×5mm QFN
• Pb-Free Plus Anneal Available (RoHS Compliant)
Applications
•V
DDQ
, V
TT
, and VREF regulation for DDRAM memory
systems
- Main memory in AMD® Athlon™ and K8™, Pentium®
III, Pentium IV, Transmeta, PowerPC™, AlphaPC™, and
UltraSparc® based computer systems
• High-power tracking DC-DC regulators
PART NUMBER
TEMP
RANGE(
o
C) PACKAGE PKG. DWG. #
ISL6531CB 0 to 70 24 Lead SOIC M24.3
ISL6531CBZ
(See Note)
0 to 70 24 Lead SOIC
(Pb-free)
M24.3
ISL6531CR 0 to 70 32 Lead 5x5 QFN L32.5x5
ISL6530/31EVAL1 Evaluation Board
Add “-T” suffix for tape and reel.
NOTE: Intersil Pb-free plus anneal products employ special Pb-free material
sets; molding compounds/die attach materials and 100% matte tin plate
termination finish, which are RoHS compliant and compatible with both SnPb
and Pb-free soldering operations. Intersil Pb-free products are MSL classified
at Pb-free peak reflow temperatures that meet or exceed the Pb-free
requirements of IPC/JEDEC J STD-020.
1
2
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V
DDQ
⋅
1
2
---
V
DDQ
⋅
Data Sheet August 11, 2005 FN9053.2
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774
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