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DDR SDRAM
512MB, 1GB, 2GB Registered DIMM
Rev. 1.0 April 2006
b. Pulldown slew rate is measured under the test conditions shown in Figure 3.
Output
Test point
VDDQ
50
Figure 3 : Pulldown slew rate test load
c. Pullup slew rate is measured between (VDDQ/2 - 320 mV +/- 250 mV)
Pulldown slew rate is measured between (VDDQ/2 + 320 mV +/- 250 mV)
Pullup and Pulldown slew rate conditions are to be met for any pattern of data, including all outputs switching and only one output switching.
Example : For typical slew rate, DQ0 is switching
For minmum slew rate, all DQ bits are switching from either high to low, or low to high.
The remaining DQ bits remain the same as for previous state.
d. Evaluation conditions
Typical : 25
°C (T Ambient), VDDQ = 2.5V(for DDR266/333) and 2.6V(for DDR400), typical process
Minimum : 70
°C (T Ambient), VDDQ = 2.3V(for DDR266/333) and 2.5V(for DDR400), slow - slow process
Maximum : 0
°C (T Ambient), VDDQ = 2.7V(for DDR266/333) and 2.7V(for DDR400), fast - fast process
e. The ratio of pullup slew rate to pulldown slew rate is specified for the same temperature and voltage, over the entire temperature and voltage range.
For a given output, it represents the maximum difference between pullup and pulldown drivers due to process variation.
f. Verified under typical conditions for qualification purposes.
g. TSOPII package divices only.
h. Only intended for operation up to 266 Mbps per pin.
i. A derating factor will be used to increase tIS and tIH in the case where the input slew rate is below 0.5V/ns as shown in Table 2. The Input slew rate is
based on the lesser of the slew rates detemined by either VIH(AC) to VIL(AC) or VIH(DC) to VIL(DC), similarly for rising transitions.
j. A derating factor will be used to increase tDS and tDH in the case where DQ, DM, and DQS slew rates differ, as shown in Tables 3 & 4. Input slew rate
is based on the larger of AC-AC delta rise, fall rate and DC-DC delta rise, Input slew rate is based on the lesser of the slew rates determined by either
VIH(AC) to VIL(AC) or VIH(DC) to VIL(DC), similarly for rising transitions. The delta rise/fall rate is calculated as: {1/(Slew Rate1)} - {1/(Slew Rate2)}
For example : If Slew Rate 1 is 0.5 V/ns and slew Rate 2 is 0.4 V/ns, then the delta rise, fall rate is - 0.5ns/V . Using the table given, this
would result in the need for an increase in tDS and tDH of 100 ps.
k. Table 3 is used to increase tDS and tDH in the case where the I/O slew rate is below 0.5 V/ns. The I/O slew rate is based on the lesser on the lesser of
the AC - AC slew rate and the DC- DC slew rate. The inut slew rate is based on the lesser of the slew rates deter mined by either VIH(ac) to VIL(ac) or
VIH(DC) to VIL(DC), and similarly for rising transitions.
l. DQS, DM, and DQ input slew rate is specified to prevent double clocking of data and preserve setup and hold times. Signal transi tions through the DC
region must be monotonic.
m. In case of Registered DIMM, device operation defines Power up and Power Management.
184-pin Double Data Rate (DDR) Registered DIMMs include two new features to facilitate controlled power-up and to minimize power consumption
during low power mode. One feature is externally controlled via a system-generated RESET signal; the second is based on module detection of the
input clocks. These enhancements permit the modules to power up with SDRAM outputs in a High-Z state (eliminating risk of high current dissipations
and/or dotted I/Os), and result in the powering-down of module support devices (registers and Phase-Locked Loop) when the memory is in Self-
Refresh mode. device operation describes this more detailly.
a. Pullup slew rate is characteristized under the test conditions as shown in Figure 2.
Output
Test point
VSSQ
50
Figure 2 : Pullup slew rate test load
15.0 System Notes: