EDE2508ACSE Datasheet, PDF (47/81 Pages) Elpida Memory – 256M bits DDR2 SDRAM

EDE2508ACSE, EDE2516ACSE
ODT (On Die Termination)
On Die Termination (ODT), is a feature that allows a DRAM to turn on/off termination resistance for each DQ, DQS,
/DQS, RDQS, /RDQS, and DM signal via the ODT control pin. The ODT feature is designed to improve signal
integrity of the memory channel by allowing the DRAM controller to independently turn on/off termination resistance
for any or all DRAM devices.
The ODT function is turned off and not supported in self-refresh mode.
VDDQ
VDDQ
VDDQ
E sw1
sw2
sw3
O DRAM
input
L^buffer
Rval1
Rval2
Rval1
Rval2
Rval3
Rval3
Input
Pin
/CK
CK
Command
ODT
Rtt
sw1
sw2
sw3
VSSQ
VSSQ
VSSQ
P_{Switch sw1, sw2 or sw3 is enabled by ODT pin.}
Selection between sw1, sw2 or sw3 is determined by Rtt (nominal) in EMRS
Termination included on all DQs, DM, DQS, /DQS, RDQS and /RDQS pins.
Target Rtt (Ω) = (Rval1) / 2, (Rval2) / 2 or (Rval3) / 2
r^{Functional Representation of ODT}
od _tAOFD
EMRS
uct _{Old setting}
NOP
tMOD (max.)
tMOD (min.)
Updating
tIS
New Setting
Note: tAOFD must be met before issuing EMRS command. ODT must remain low for the entire duration of tMOD window.
ODT update Delay Timing
Preliminary Data Sheet E0948E30 (Ver. 3.0)
47