Rev. 1.7 / Nov 2011
General notes, which may apply for all AC parameters
1. Slew Rate Measurement Levels
a. Output slew rate for falling and rising edges is measured between VTT - 250 mV and VTT + 250 mV for single ended
For differential signals (e.g. DQS - DQS) output slew rate is measured between DQS - DQS = -500 mV and DQS
- DQS = +500mV. Output slew rate is guaranteed by design, but is not necessarily tested on each device.
b. Input slew rate for single ended signals is measured from dc-level to ac-level: from VIL(dc) to VIH(ac) for
rising edges and from
VIH(dc) and VIL(ac) for falling edges.
For differential signals (e.g. CK - CK) slew rate for rising edges is measured from CK - CK = -250 mV to CK - CK =
+500 mV(250mV to -500 mV for falling egdes).
c. VID is the magnitude of the difference between the input voltage on CK and the input voltage on CK, or between
DQS and DQS for differential strobe.
2. DDR2 SDRAM AC timing reference load
The following figure represents the timing reference load used in defining the relevant timing parameters of the part.
It is not intended to be either a precise representation of the typical system environment nor a depiction of the actual
load presented by a production tester. System designers will use IBIS or other simulation tools to correlate the timing
reference load to a system environment. Manufacturers will correlate to their production test conditions (generally a
coaxial transmission line terminated at the tester electronics).
The output timing reference voltage level for single ended signals is the crosspoint with VTT. The output timing refer-
ence voltage level for differential signals is the crosspoint of the true (e.g. DQS) and the complement (e.g. DQS)
3. DDR2 SDRAM output slew rate test load
Output slew rate is characterized under the test conditions as shown below.
4. Differential data strobe
DDR2 SDRAM pin timings are specified for either single ended mode or differential mode depending on the setting of
the EMRS “Enable DQS” mode bit; timing advantages of differential mode are realized in system design. The method
by which the DDR2 SDRAM pin timings are measured is mode dependent. In single
VTT = VDDQ/2
AC Timing Reference Load
VTT = VDDQ/2
Slew Rate Test Load