MT41J256M4 Datasheet, PDF (54/181 Pages) Micon Design Technology Corporation – 1Gb: x4, x8, x16 DDR3 SDRAM

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
performed. Output specifications refer to the default output driver unless specifically
stated otherwise. A functional representation of the output buffer is shown in Figure 29
on page 54. 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 percent; x = 34Ω or 40Ω with y = 7 or 6, respec-
tively)
The individual pull-up and pull-down resistors (RONPU and RONPD) are defined as
follows:
• RONPU = (VDDQ - VOUT)/|IOUT|, when RONPD is turned off
• RONPD = (VOUT)/|IOUT|, when RONPU is turned off
Figure 29: Output Driver
Chip in drive mode
Output driver
To
other
circuitry
such as
RCV, . . .
I_PU
RONPU
RONPD
I_PD
VDDQ
IOUT
DQ
VOUT
VSSQ
34Ω Output Driver Impedance
The 34Ω driver (MR1[5, 1] = 01) is the default driver. Unless otherwise stated, all timings
and specifications listed herein apply to the 34Ω driver only. Its impedance RON is
defined by the value of the external reference resistor RZQ as follows: RON34 = RZQ/7
(with nominal RZQ = 240Ω ±1 percent) and is actually 34.3Ω ±1 percent. The 34Ω output
driver impedance characteristics are listed in Table 35 on page 55.
PDF: 09005aef826aa906/Source: 09005aef82a357c3
1Gb_DDR3_3.fm - Rev. D 8/1/08 EN
54
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