LP2994M National Semiconductor, LP2994M Datasheet - Page 14

• Manufacturer Part Number: LP2994M
• Description: DDR Termination Regulator
• Manufacturer: National Semiconductor

www.national.com
Typical Application Circuits
with the DDR-SDRAM DIMMs mounted on modules. As a
result bulk aluminum electrolytic capacitors in the range of
1000uF are typically used.
PCB Layout Considerations
1. The input capacitor for the power rail should be placed
2. V
3. V
(Continued)
as close as possible to the PVIN pin.
at the point where regulation is required. For mother-
board applications an ideal location would be at the
center of the termination bus.
at either the DIMM or the Chipset. This provides the
most accurate point for creating the reference voltage.
SENSE
DDQ
can be connected remotely to the V
should be connected to the V
TT
termination bus
DDQ
rail input
14
4. For improved thermal performance excessive top side
5. Care should be taken when routing the V
copper should be used to dissipate heat from the pack-
age. Numerous vias from the ground connection to the
internal ground plane will help. Additionally these can be
located underneath the package if manufacturing stan-
dards permit.
avoid noise pickup from switching I/O signals. A 0.1uF
ceramic capacitor located close to the V
be used to filter any unwanted high frequency signal.
This can be an issue especially if long V
used.
SENSE
SENSE
SENSE
traces are
can also
trace to