Datasheet

On-Die Termination
ODT (On-Die Termination) is a feature of the DDR4 SDRAM that allows the DRAM to change termination
resistance for x16 configuration, ODT is applied to each DQ0-15, UDQS, UDQS#, LDQS, LDQS#, UDM# and
LDM# signal. The ODT feature is designed to improve signal integrity of the memory channel by allowing the
DRAM controller to independently change termination resistance for any or all DRAM devices.
The ODT feature is turned off and not supported in Self-Refresh mode. A simple functional representation of
the DRAM ODT feature is shown below.
To other circuitry
like
DQ, DQS, DM,
ODT
VDDQ
RTT
Switch
Figure 162. Functional Representation of ODT
The switch is enabled by the internal ODT control logic, which uses the external ODT pin and Mode Register
Setting and other control information, see below. The value of R
TT
is determined by the settings of mode
register bits (see Mode Register). The ODT pin will be ignored if the mode register MR1 is programmed to
disable R
TT_NOM
(MR1 A [10:8] = 000) and in self refresh mode.
AS4C256M16D4
Confidential
- 145 of 201 -
Rev.1.0 Aug.2019