PRELIMINARY
CM3121
Dual Linear Voltage Regulator for DDR-I and DDR-II Memory
Features
Product Description
The CM3121 provides an integrated power solution for
DDR-I and DDR-II memory systems in consumer electron-
ics applications. The CM3121 is ideal for a 2.8V to 3.6V
supply for DDR-I memory and 2.2V to 2.8V for DDR-II mem-
ory. The CM3121 features two independent linear regula-
•
Fully integrated power solution for DDR memory
ICs
•
•
Ideal for DDR-I (2.5V
Lowest system cost and smallest footprint with just
two external output capacitors
) and DDR-II (1.8V
)
DDQ
DDQ
tors for V
and V
supply regulation. The default
DDQ
TT
•
Two linear regulators:
voltage for V
is 2.5V. The V
regulator SENSE pin
- V
regulator with a maximum output current
DDQ
DDQ
DDQ
allows for setting V
in the 2.2V to 2.8V range, or DDR-II
of 1.5A shared by DRAM and V regulator
DDQ
TT
memories from 1.7V to 1.9V. The V regulator output is
TT
- source-sink V regulator with maximum out-
TT
always half the V
voltage, derived internally. A capacitor
DDQ
put current of 0.5A (DDR-I) or 0.3A (DDR-II)
Fault output indicates overcurrent condition in
either regulator, under voltage lock-out and over-
temperature condition
Reverse current protection if host is powered off
PSOP-8 package with integrated heat spreader
Lead-free versions available
should be connected to each of the two outputs.
•
When EN_DDR is set high, the two DDR regulators are dis-
abled to minimize overall system power dissipation such as
when memory is in standby.
•
•
•
The FAULT pin goes low whenever either of the two regula-
tors goes into current limit mode, the input voltage drops too
far or if overtemp occurs.
Applications
The CM3121 is available in a PSOP-8 package that has
excellent thermal dissipation. It is available with optional
lead-free finishing.
•
DDR-I and DDR-II memory power for:
− Set Top Boxes, DVD Players, Games
− Digital TVs, Flat Panel Displays
− Printers, Digital Projectors
.
− Embedded systems
− Communications systems
Typical Application Circuit
Circuit Schematic
2.8V to 3.3V
V
CC
VDDQ
VCC
REGULATOR
VREF
VDDQ
REGULATOR
VDDQ
V
DDQ
C
VREF
CC
VDDQ = 2.5V
V
DDQ
SENSE
VDDQ
SENSE_ V
SENSE
DDQ
DDQ
V
EN_DDR
C
DDQ
EN_DDR
Enable DDR
Memory #
DDR
MEMORY
VTT
REGULATOR
R
VTT
REGULATOR
R
VTT
VTT=1.25V
V
VTT
TT
R
R
SENSE VTT
SENSE V
TT
C
TT
SENSE_V
FAULT
TT
CPU
CORE
+ I/O
CURRENT LIMIT
OVERTEMP
LOW INPUT
FAULT
CURRENT LIMIT
OVERTEMP
LOW INPUT
GND
GND
© 2004 California Micro Devices Corp. All rights reserved.
11/12/04 430 N. McCarthy Blvd., Milpitas, CA 95035-5112
●
Tel: 408.263.3214
●
Fax: 408.263.7846
●
www.calmicro.com
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