
Input Slew Rate Derating
For all input signals, the total tIS (setup time) and tIH (hold time) required is calculated
by adding the data sheet tIS (base) and tIH (base) value to the
ΔtIS and ΔtIH derating
value, respectively. Example: tIS (total setup time) = tIS (base)
+ ΔtIS.
tIS, the nominal slew rate for a rising signal, is defined as the slew rate between the last
crossing of VREF(DC) and the first crossing of VIH(AC)min. Setup nominal slew rate (tIS) for
a falling signal is defined as the slew rate between the last crossing of VREF(DC) and the
first crossing of VIL(AC)max.
If the actual signal is always earlier than the nominal slew rate line between shaded
“VREF(DC) to AC region,” use the nominal slew rate for the derating value (Figure 23 If the actual signal is later than the nominal slew rate line anywhere between the sha-
ded “VREF(DC) to AC region,” the slew rate of a tangent line to the actual signal from the
tIH, the nominal slew rate for a rising signal, is defined as the slew rate between the last
crossing of VIL(DC)max and the first crossing of VREF(DC). tIH, nominal slew rate for a fall-
ing signal, is defined as the slew rate between the last crossing of VIH(DC)min and the first
crossing of VREF(DC).
If the actual signal is always later than the nominal slew rate line between shaded “DC
to VREF(DC) region,” use the nominal slew rate for the derating value (Figure 25 If the actual signal is earlier than the nominal slew rate line anywhere between shaded
“DC to VREF(DC) region,” the slew rate of a tangent line to the actual signal from the DC
Although the total setup time might be negative for slow slew rates (a valid input signal
will not have reached VIH[AC]/VIL[AC] at the time of the rising clock transition), a valid
input signal is still required to complete the transition and reach VIH(AC)/VIL(AC).
(page 58), the derating values may obtained by linear interpolation.
1Gb: x4, x8, x16 DDR2 SDRAM
Input Slew Rate Derating
PDF: 09005aef821ae8bf
1GbDDR2.pdf – Rev. S 10/09 EN
56
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