CM3109
2A Sink/Source Regulator for Front Side Bus and
DDR Memory Bus Termination
Features
Product Description
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Ideal for both PC Front Side Bus and DDR memory
applications
Sinks and sources 2A
Over current protection
Over temperature protection
Shutdown function
Integrated power MOSFETs
Excellent accuracy (0.5% of load regulation)
Minimum external components
8 pin PSOP package
The CM3109 is a sinking and sourcing regulator specif-
ically designed for series-parallel bus termination for
high speed chip set buses as well as DDR memory
systems. It can source and sink current up to 2A with
V
TT
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high accuracy of 0.5 %. The V
output voltage is
TT
selectable by V
SEL and FSBSEL pins. The
DDQ
V
SEL pin controls whether the CM3109 is in DDR
DDQ
memory mode with V = V
/2, or in FSB mode. In
DDQ
TT
FSB mode, FSBSEL controls whether V is 1.225V or
TT
1.45V. This allows the same chip to be used in two dif-
ferent circuits on PC motherboards that support both
Northwood and Prescott processors.
Lead-free version available
Applications
The CM3109 requires no external components to use
the GMCH Enable signal in Intel chipset or correspond-
ing signals for other chip sets when powering up the
PC. For the boards which support Suspend to RAM
(STR) functionality, CM3109 provides a shutdown (SD)
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PC Front Side Bus termination regulator
DDR Memory termination regulator
Active termination buses
Graphics card DDR memory termination
pin. When SD is set low, V will be in tri-state mode,
TT
causing the output to go high impedance. In this mode,
CM3109 power is saved by significantly reducing the
quiescent current.
The CM3109 provides over current and over tempera-
ture protection. These features protect the chip from
excessive heating due to high current and high temper-
ature. The CM3109 is housed in an 8-pin PSOP pack-
age and is available with optional lead-free finishing.
Simplified Electrical
V
V
SEL FSBSEL
V
DDQ
CC
DDQ
Schematic
Output
Select
Over Temp
Over Current
Reference
SD
Driver
V
TT
V
SENSE
GND
© 2004 California Micro Devices Corp. All rights reserved.
01/15/04 430 N. McCarthy Blvd., Milpitas, CA 95035-5112
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Tel: 408.263.3214
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Fax: 408.263.7846
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www.calmicro.com
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