Datasheet

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ODT (On Die Termination)
On Die Termination (ODT) is a feature that allows a DRAM to turn on/off termination resistance for each DQ,
UDQS/UDQS#, LDQS/LDQS#, UDM, and LDM 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 supported for ACTIVE and STANDBY modes. It is turned off and not supported in SELF
REFRESH mode.
Figure 5. Functional representation of ODT
SW1
Rval1
V
DDQ
SW1
Rval1
V
SSQ
SW3
Rval3
V
DDQ
SW3
Rval3
V
SSQ
SW2
Rval2
V
DDQ
SW2
Rval2
V
SSQ
Input
pin
DRAM
Input
Buffer
Switch (sw1, sw2, sw3) is enabled by ODT pin.
Selection among sw1, sw2, and sw3 is determined by “Rtt (nominal)” in EMR.
Termination included on all DQs, DM, DQS, and DQS# pins
Table 11. ODT DC Electrical Characteristics
Parameter/Condition
Symbol
Min.
Nom.
Max.
Unit
Note
Rtt effective impedance value for EMRS(A6,A2)=0,1;75Ω
Rtt1(eff)
60
75
90
Ω
1
Rtt effective impedance value for EMRS(A6,A2)=1,0;150Ω
Rtt2(eff)
120
150
180
Ω
1
Rtt effective impedance value for EMRS(A6,A2)=1,1;50Ω
Rtt3(eff)
40
50
60
Ω
1
Rtt mismatch tolerance between any pull-up/pull-down pair
Rtt(mis)
-6
-
6
%
2
NOTE 1: Measurement Definition for Rtt(eff): Apply V
IH
(ac) and V
IL
(ac) to test pin separately, then measure
current I(V
IH
(ac)) and I(V
IL
(ac)) respectively.
() ()
IH IL
IH IL
Vac Vac
Rtt(eff)=
I(V (ac))-I(V (ac))
NOTE 2: Measurement Definition for Rtt (mis): Measure voltage (VM) at test pin (midpoint) with no load.
1100%




DDQ
2xVM
Rtt(mis)=
V
AS4C64M16D2A-25BIN
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Rev.1.1 October 2017