Ver: 2.3
May 16, 2006
TEL: 886-3-5788833
http://www.gmt.com.tw
11
G2996
Global Mixed-mode Technology Inc.
In Figure 5 & 6, they are the application configurations
of DDR-II SDRAM bus terminations. Figure 5 is the
typical application scheme of DDR-II SDRAM. With the
separate VDDQ pin and an internal resistor divider, it
is possible to use the G2996 in applications utilizing
DDR-II memory. Figure 6 is used to increase the driv-
ing capability. The risk is the same as figure 4.
Figure 7 & 8 are used to scale the VTT to the wanted
value when the standard voltages of SSTL-2 do not
meet the requirements. Using R1 & R2, figure 7 can
shift VTT up to VDDQ/2 * (1+R1/R2) and figure 8 can
shift VTT down to VDDQ/2 * (1-R1/R2).
+
V
DDQ
AV
IN
V
SENSE
PV
IN
V
TT
GND
V
TT
V
DD
C
IN
Figure 7. Increasing VTT by Level Shifting
C
OUT
V
DDQ
R1
R2
+
V
DDQ
AV
IN
V
SENSE
PV
IN
V
TT
GND
V
TT
V
DD
C
IN
Figure 8. Decreasing VTT by Level Shifting
C
OUT
V
DDQ
R1
R2
+
V
DDQ
AV
IN
V
SENSE
PV
IN
V
TT
GND
V
TT
V
DD
C
IN
Figure 7. Increasing VTT by Level Shifting
C
OUT
V
DDQ
R1
R2
+
V
DDQ
AV
IN
V
SENSE
PV
IN
V
TT
GND
V
TT
V
DD
C
IN
Figure 7. Increasing VTT by Level Shifting
C
OUT
V
DDQ
R1
R2
+
V
DDQ
AV
IN
V
SENSE
PV
IN
V
TT
GND
V
TT
V
DD
C
IN
Figure 8. Decreasing VTT by Level Shifting
C
OUT
V
DDQ
R1
R2
+
V
DDQ
AV
IN
V
SENSE
PV
IN
V
TT
GND
V
TT
V
DD
C
IN
Figure 8. Decreasing VTT by Level Shifting
C
OUT
V
DDQ
R1
R2
+
SD
V
REF
V
DDQ
AV
IN
V
SENSE
PV
IN
V
TT
GND
V
TT=0.9V
V
REF=0.9V
V
DDQ=1.8V
AV
IN=1.8V or 5.5V
SD
C
IN
Figure 5. Recommended DDR-II Termination
C
OUT
C
REF
PV
IN=1.8V
+
SD
V
REF
V
DDQ
AV
IN
V
SENSE
PV
IN
V
TT
GND
V
TT=0.9V
V
REF=0.9V
V
DDQ=1.8V
AV
IN=3.3V or 5.5V
SD
C
IN
Figure 6. DDR-II Termination with higher voltage rails
C
OUT
C
REF
PV
IN=3.3V
+
SD
V
REF
V
DDQ
AV
IN
V
SENSE
PV
IN
V
TT
GND
V
TT=0.9V
V
REF=0.9V
V
DDQ=1.8V
AV
IN=1.8V or 5.5V
SD
C
IN
Figure 5. Recommended DDR-II Termination
C
OUT
C
REF
PV
IN=1.8V
+
SD
V
REF
V
DDQ
AV
IN
V
SENSE
PV
IN
V
TT
GND
V
TT=0.9V
V
REF=0.9V
V
DDQ=1.8V
AV
IN=3.3V or 5.5V
SD
C
IN
Figure 6. DDR-II Termination with higher voltage rails
C
OUT
C
REF
PV
IN=3.3V