LP2996LQ National Semiconductor, LP2996LQ Datasheet - Page 14

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

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Typical Application Circuits
LEVEL SHIFTING
If standards other than SSTL-2 are required, such as
SSTL-3, it may be necessary to use a different scaling factor
than 0.5 times V
eral options are available to scale the output to any voltage
required. One method is to level shift the output by using
Conversely, the R2 resistor can be placed between V
and V
reference voltage of VDDQ/2. The equations relating VTT
and the resistors can be seen below:
DDQ
to shift the V
DDQ
for regulating the output voltage. Sev-
TT
output lower than the internal
FIGURE 9. DDR-II Termination with higher voltage rails
FIGURE 11. Decreasing VTT by Level Shifting
FIGURE 10. Increasing VTT by Level Shifting
(Continued)
SENSE
14
feedback resistors from V
been illustrated in Figures 10 and 11. Figure 10 shows how
to use two resistors to level shift V
reference voltage of VDDQ/2. To calculate the exact voltage
at V
TT
the following equation can be used.
V
V
TT
TT
= VDDQ/2 ( 1 + R1/R2)
= VDDQ/2 (1 - R1/R2)
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TT
to the V
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TT
SENSE
above the internal
pin. This has