LP2996LQ National Semiconductor, LP2996LQ Datasheet - Page 16

• Manufacturer Part Number: LP2996LQ
• Description: DDR Termination Regulator
• Manufacturer: National Semiconductor

www.national.com
Typical Application Circuits
In most PC applications an extensive amount of decoupling
is required because of the long interconnects encountered
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.
2. V
3. V
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.
The input capacitor for the power rail should be placed
SENSE
DDQ
can be connected remotely to the V
should be connected to the V
FIGURE 14. Typical SSTL-2 Application Circuit for Motherboards
TT
termination bus
DDQ
(Continued)
rail input
16
4. For improved thermal performance excessive top side
5. Care should be taken when routing the V
6. 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
used to filter any unwanted high frequency signal. This
can be an issue especially if long
ceramic capacitor for improved performance. This ca-
pacitor should be located as close as possible to the
V
REF
REF
pin.
should be bypassed with a 0.01 µF or 0.1 µF
20057519
SENSE
SENSE
traces are used.
SENSE
can also be
trace to