![](http://datasheet.mmic.net.cn/200000/MT41J128M16HA-107-D_datasheet_15084792/MT41J128M16HA-107-D_63.png)
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
stated otherwise. A functional representation of the output buffer is shown below. The
output driver impedance Ron is defined by the value of the external reference resistor
RZQ as follows:
RON,x = RZQ/y (with RZQ = 240Ω ±1%; x = 34Ω or 40Ω with y = 7 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 27: Output Driver
RON(PU)
RON(PD)
Output driver
To
other
circuitry
such as
RCV, . . .
Chip in drive mode
VDDQ
VSSQ
IPU
IPD
IOUT
VOUT
DQ
2Gb: x4, x8, x16 DDR3 SDRAM
Output Driver Impedance
PDF: 09005aef826aaadc
2Gb_DDR3_SDRAM.pdf – Rev. K 04/10 EN
63
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