1Gb: x4, x8, x16 DDR3 SDRAM
On-Die Termination (ODT)
On-Die Termination (ODT)
On-die termination (ODT) is a feature that enables the DRAM to enable/disable and
turn on/off termination resistance for each DQ, DQS, DQS#, and DM for the x4 and x8
configurations (and TDQS, TDQS# for the x8 configuration, when enabled). ODT is ap-
plied to each DQ, UDQS, UDQS#, LDQS, LDQS#, UDM, and LDM signal for the x16 con-
figuration.
ODT is designed to improve signal integrity of the memory channel by enabling the
DRAM controller to independently turn on/off the DRAM’s internal termination resist-
ance for any grouping of DRAM devices. ODT is not supported during DLL disable
mode (simple functional representation shown below). The switch is enabled by the in-
ternal ODT control logic, which uses the external ODT ball and other control informa-
tion.
Figure 109: On-Die Termination
ODT
VDDQ/2
To other
circuitry
such as
RCV,
RTT
Switch
DQ, DQS, DQS#,
DM, TDQS, TDQS#
. . .
Functional Representation of ODT
The value of RTT (ODT termination resistance value) is determined by the settings of
several mode register bits (see Table 80 (page 196)). The ODT ball is ignored while in
self refresh mode (must be turned off prior to self refresh entry) or if mode registers
MR1 and MR2 are programmed to disable ODT. ODT is comprised of nominal ODT and
dynamic ODT modes and either of these can function in synchronous or asynchronous
mode (when the DLL is off during precharge power-down or when the DLL is synchro-
nizing). Nominal ODT is the base termination and is used in any allowable ODT state.
Dynamic ODT is applied only during writes and provides OTF switching from no RTT or
RTT,nom to RTT(WR).
The actual effective termination, RTT(EFF), may be different from RTT targeted due to
nonlinearity of the termination. For RTT(EFF) values and calculations, see ODT Charac-
teristics (page 50).
Nominal ODT
ODT (NOM) is the base termination resistance for each applicable ball; it is enabled or
disabled via MR1[9, 6, 2] (see Mode Register 1 (MR1) Definition), and it is turned on or
off via the ODT ball.
PDF: 09005aef826aa906
1Gb_DDR3_SDRAM.pdf - Rev. L 03/13 EN
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