IC61C6416 Datasheet, PDF (24/80 Pages) Integrated Circuit Solution Inc – 64K X 16 HIGH-SPEED CMOS STATIC RAM

HYB18T256324F–[16/20/22]
256-Mbit DDR SGRAM
Functional Description
3.3
Programmable impedance output drivers and active terminations
3.3.1 GDDR3 IO Driver and Termination
The GDDR3 SGRAM is equipped with programmable
impedance output buffers and active terminations. This
allows the user to match the driver impedance to the
system impedance.
To adjust the impedance of DQ<0:31> and
RDQS<0:3> , an external precision resistor (ZQ) is
connected between the ZQ pin and VSS. The value of
the resitor must be six times the value of the desired
impedance. For example, a 240Ω resistor is required
for an output impedance of 40Ω. The range of ZQ is
210Ω to 270Ω, giving an output impedance range of
35Ω to 45Ω (one sixth the value of ZQ within 10%).
RES, CLK and CLK are not internally terminated.
The value of ZQ is used to calibrate the internal DQ
termination resistors of DQ<0:31>, WDQS<0:3> and
DM<0:3>. The two termination values that are
selectable using EMRS[3:2] are ZQ / 4 and ZQ / 2.
The value of ZQ is also used to calibrate the internal
address command termination resistors. The inputs
terminated in this manner are A<0:11>, CKE, CS, RAS,
CAS, WE. The two termination values that are
selectable upon power up (CKE latched a the LOW to
HIGH transition of RES) are ZQ/2 and ZQ.
The signals RES and CLK/CLK are not internally
terminated.
If no resistance is connected to ZQ, an internal default
value of 240Ω will be used. In this case, no calibration
will be performed.
Read to
other Rank
VDDQ
ZQ/4 or ZQ/2
Terminator when
receiving
Output Data
Read Data
Enable
DQ
ZQ/6 Driver
when transmitting
VSSQ
Figure 6 Output Driver simplified schematic
Table 11 Range of external resistance ZQ
Parameter
Symbol min
External resistance value
ZQ
210
nom
240
max
270
Unit Notes
Ω
Table 12 Termination types and activation
Ball
CLK, CLK, RDQS<0:3>, ZQ, RES
CKE, CS, RAS, CAS, WE, BA<0:1>, A<0:11>
DM<0:3>, WDQS<0:3>,
DQ<0:31>
Termination type
No termination
Add / CMDs
DQ
DQ
Termination activation
Always ON
Always ON
CMD bus snooping
Data Sheet
24
Rev. 1.11, 04-2005
10292004-DOXT-FS0U