HYB18T256400AF Datasheet, PDF (81/90 Pages) Infineon Technologies AG – 256 Mbi t DDR2 SDRAM

HYB18T256400/800/160AF
256Mb DDR2 SDRAM
8. Reference Loads, Setup & Hold Timing Definition and Slew Rate Derating
8.1 Reference Load for Timing Measurements
The figure represents the timing reference load used in defining the relevant timing parameters of the device. It is
not intended to either a precise representation of the typical system environment nor a depiction of the actual load
presented by a production tester. System designers should use IBIS or other simulation tools to correlate the tim-
ing reference load to a system environment. Manufacturers correlate to their production test conditions, generally
a coaxial transmission line terminated at the tester electronics. This reference load is also used for output slew
rate characterization.
CK, CK
VDDQ
DUT
DQ
DQS
DQS
RDQS
RDQS
25 Ohm
Vtt = VDDQ / 2
Timing Reference Points
The output timing reference voltage level for single ended signals is the crosspoint with VTT.
The output timing reference voltage level for differential signals is the crosspoint of the true (e.g. DQS) and the
complement (e.g. DQS) signal.
8.2 Slewrate Measurements
8.2.1 Output Slewrate
With the reference load for timing measurements 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) out-
put slew rate is measured between DQS - DQS = - 500 mV and DQS - DQS = + 500 mV. Output slew rate is veri-
fied by design and characterisation, but not tested during production.
8.2.2 Input Slewrate - Differential signals
Input slewrate for differential signals (CK / CK, DQS / DQS, RDQS / RDQS) for rising edges are measured from
f.e. CK - CK = -250 mV to CK - CK = + 500 mV and from CK - CK = +250 mV to CK - CK = - 500mV for falling
edges.
8.2.3 Input Slewrate - Single ended signals
Input slew rate for single ended signals (other than tis, tih, tds and tdh) are measured from dc-level to ac-level:
VREF -125 mV to VREF + 250 mV for rising edges and from VREF + 125 mV to VREF - 250 mV for falling edges.
For slew rate definition of the input and data setup and hold parameters see section 8.3 of this datasheet.
Page 81
Rev. 1.02 May 2004
INFINEON Technologies