1Gb: x4, x8, x16 DDR3 SDRAM
Output Driver Impedance
Output Driver Impedance
The output driver impedance is selected by MR1[5,1] during initialization. The selected
value is able to maintain the tight tolerances specified if proper ZQ calibration is per-
formed. Output specifications refer to the default output driver unless specifically sta-
ted otherwise. A functional representation of the output buffer is shown below. The out-
put driver impedance RON is defined by the value of the external reference resistor RZQ
as follows:
• RON,x = RZQ/y (with RZQ = 24±Ω rꢂꢉꢊꢋx ꢋꢇꢆΩ or 4±Ω with y = 0 or 6, respectively)
The individual pull-up and pull-down resistors RON(PU) and RON(PD) are defined as fol-
lows:
• RON(PU) = (VDDQ - VOUT)/|IOUT|, when RON(PD) is turned off
• RON(PD) = (VOUT)/|IOUT|, when RON(PU) is turned off
Figure 28: Output Driver
Chip in drive mode
Output driver
VDDQ
IPU
To
other
RON(PU)
circuitry
such as
RCV, . . .
DQ
IOUT
RON(PD)
VOUT
IPD
VSSQ
PDF: 09005aef826aa906
1Gb_DDR3_SDRAM.pdf - Rev. L 03/13 EN
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