EDJ8216E5MB Datasheet, PDF (137/142 Pages) Elpida Memory – 8G bits DDR3L SDRAM, DDP

EDJ8216E5MB
ZQ Calibration
ZQ calibration command is used to calibrate DRAM RON and ODT values. DDR3 SDRAM needs longer time to
calibrate RON and ODT at initialization and relatively smaller time to perform periodic calibrations.
ZQCL command is used to perform the initial calibration during power-up initialization sequence. This command may
be issued at any time by the controller depending on the system environment. ZQCL command triggers the
calibration engine inside the DRAM and once calibration is achieved the calibrated values are transferred from
calibration engine to DRAM I/O which gets reflected as updated RON and ODT values.
The first ZQCL command issued after reset is allowed a timing period of tZQinit to perform the full calibration and the
transfer of values. All other ZQCL commands except the first ZQCL command issued after RESET is allowed a
timing period of tZQoper.
ZQCS command is used to perform periodic calibrations to account for voltage and temperature variations. A shorter
timing window is provided to perform the calibration and transfer of values as defined by timing parameter tZQCS.
One ZQCS command can effectively correct a minimum of 0.5% (ZQCorrection) of RON and RTT impedance error
within 64nCK for all speed bins assuming the maximum sensitivities specified in the ‘Output Driver Voltage and
Temperature Sensitivity’ and ‘ODT Voltage and Temperature Sensitivity’ tables. The appropriate interval between
ZQCS commands can be determined from these tables and other application-specific parameters. One method for
calculating the interval between ZQCS commands, given the temperature (Tdriftrate) and voltage (Vdriftrate) drift
rates that the SDRAM is subject to in the application, is illustrated. The interval could be defined by the following
formula:
ZQCorrection
(Tsens × Tdriftrate) + (Vsens × Vdriftrate)
where TSens = max(dRTTdT, dRONdTM) and VSens = max(dRTTdV, dRONdVM) define the SDRAM temperature
and voltage sensitivities.
For example, if TSens = 1.5%/C, VSens = 0.15%/mV, Tdriftrate = 1C/sec and Vdriftrate = 15mV/sec, then the
interval between ZQCS commands is calculated as:
0.5
(1.5 × 1) + (0.15 × 15) ^{= 0.133 ≈ 128ms}
No other activities should be performed on the DRAM channel by the controller for the duration of tZQinit, tZQoper or
tZQCS. The quiet time on the DRAM channel allows in accurate calibration of RON and ODT. Once DRAM
calibration is achieved the DRAM should disable ZQ current consumption path to reduce power.
All banks must be precharged and tRP met before ZQCL or ZQCS commands are issued by the controller.
ZQ calibration commands can also be issued in parallel to DLL lock time when coming out of self-refresh. Upon self-
refresh exit, DDR3 SDRAM will not perform an I/O calibration without an explicit ZQ calibration command. The
earliest possible time for ZQ Calibration command (short or long) after self-refresh exit is tXS.
In systems that share the ZQ resistor between devices, the controller must not allow any overlap of tZQoper, tZQinit
or tZQCS between the devices.
CK
Command
ZQCL
NOP/DESL
Valid
ZQCS NOP/DESL Valid
A10
Address
A10 = H
X
A10 = L
X
CKE
DQ Bus*²
tZQinit or tZQ oper
Hi-Z
Activities
tZQCS
Hi-Z
Activities
Notes: 1. CKE must be continuously registered high during the calibration procedure.
2. ODT must be disabled via ODT signal or MRS during calibration procedure.
3. All device connected to DQ bus should be High impedance during calibration.
ZQ Calibration
Data Sheet E1826E30 (Ver. 3.0)
137