W632GU6NB
Publication Release Date: Aug. 20, 2018
Revision: A01
- 79 -
8.18.2 ZQ Calibration Timing
T0
T1
Ta1
CK#
CK
ZQCL
NOP
Ta3
NOP
VALID
ZQCS
Command
VALID
Ta0
A10
Tb1
Tc0
NOP
Address
t
ZQinit or
t
ZQoper
Tc1
Tc2
NOP
NOP
Ta2
Tb0
VALID
NOP
VALID
VALID
VALID
VALID
VALID
VALID
VALID
VALID
CKE
ODT
Hi-Z
ACTIVITIES
Hi-Z
VALID
VALID
VALID
VALID
ACTIVITIES
DQ Bus
t
ZQCS
TIME BREAK
DON'T CARE
*1
*2
*3
*1
*2
*3
Notes:
1. CKE must be continuously registered high during the calibration procedure.
2. On-die termination must be disabled via the ODT signal or MRS during the calibration procedure.
3. All devices connected to the DQ bus should be high impedance during the calibration procedure.
Figure 72
– ZQ Calibration Timing
8.18.3 ZQ External Resistor Value, Tolerance, and Capacitive loading
In order to use the ZQ Calibration function, a 240 ohm ± 1% tolerance external resistor must be
connected between the ZQ pin and ground. The single resistor can be used for each SDRAM or one
resistor can be shared between two SDRAMs if the ZQ calibration timings for each SDRAM do not
overlap. The total capacitive loading on the ZQ pin must be limited (See section 10.11
on page 120).