Rev. 1.7 / Nov. 2011
General notes, which may apply for all AC parameters
1. 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 simula-
tion 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 tim-
ing reference voltage level for differential signals is the crosspoint of the true (e.g. DQS) and the complement
(e.g. DQS) signal.
2. 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 signals. 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 VREF - 125 mV to
VREF + 250 mV for rising edges and from VREF + 125 mV and VREF - 250 mV 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 edges).
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.
3. DDR2 SDRAM output slew rate test load
Output slew rate is characterized under the test conditions as shown below.
VTT = VDDQ/2
AC Timing Reference Load
VTT = VDDQ/2
Slew Rate Test Load