i.MX6 DDR3 Drive Strength and ODT Settings When Using ZQ Calibration

[RobertC]

Hello,

From what I read, "ZQ calibration is a process that tunes the DRAM and MMDC I/O Pad output drivers (drive strength) and ODT values across changes in process, voltage, and temperature."

If periodic ZQ calibration is used, do I still need the set the drive strength in the IOMUX pad setting registers?  Do I still need to set the ODT values in MMDC_MPODTCTRL register?

Thanks,
RC

[igorpadykov]

Hi Ron

>f periodic ZQ calibration is used, do I still need the set the drive strength in the IOMUX pad setting >registers? Do I still need to set the ODT values in MMDC_MPODTCTRL register?

no. After ddr test successfully passed and performed sect.3.2.1 Changing the DCD table for i.MX DDR initialization  i.MX Porting Guide​, no need for additional changes.

https://community.nxp.com/t5/i-MX-Processors-Knowledge-Base/i-MX-6-7-DDR-Stress-Test-Tool/ta-p/11082...

Best regards
igor

[RobertC]

Hi igor,

We did a simulation for the layout.  For clock, address and commands, the results of the simulation suggest 48 ohm drive strength.  For data, the simulation suggests 40 ohm drive strength with ODT40.

These values are different than the values used in the Programming Aid.  Considering the periodic ZQ calibration is enabled, the drive strength and ODT should be adjusted automatically on the fly.  Should I change the DSE values and the ODT values according to the simulation?  Does it matter?

Signal	Simulation Suggestion	Programming Aid	Register
Clock	DSE = 101 (48 ohm)	DSE = 110 (40 ohm)	IOMUXC_SW_PAD_CTL_PAD
Address	DSE = 101 (48 ohm)	DSE = 110 (40 ohm)	IOMUXC_SW_PAD_CTL_PAD
Command	DSE = 101 (48 ohm)	DSE = 110 (40 ohm)	IOMUXC_SW_PAD_CTL_PAD
Data	DSE = 110 (40 ohm)	DSE = 110 (40 ohm)	IOMUXC_SW_PAD_CTL_PAD
Data	ODT = 011 (40 ohm)	ODT = 001 (120 ohm)	MPODTCTRL

Thanks,
RC

[igorpadykov]

>These values are different than the values used in the Programming Aid.

> Should I change the DSE values and the ODT values according to the simulation? Does it matter?

right, Programming Aid values are provided for NXP reference board as typical values.

So for custom board they can be changed (if needed) based on simulation results and

results from ddr test.

Best regards
igor