AM6442: Termination required for EMMC interface in TMD64EVM

Fhamitha M

Part Number: AM6442

Tool/software:

Hi,

I am performing SI analysis using the HyperLynx tool for a custom board design based on the TMD64EVM reference. While analyzing the eMMC interface, I observed that Vmax, Vmin, undershoot, and overshoot are not within the expected range. According to the AM6442 IBIS model, the driver seems to support only 40 Ω impedance, but in the TMD64EVM board the eMMC signals are routed with 50 Ω impedance without any external series termination, even though the driver supports 40 Ω. How does the TMD64EVM achieve proper signal integrity in this case? I also tried 10 Ω and 22 Ω series termination, and the results matched the expected range. Is it recommended to add an external series termination resistor in this scenario?

Regards,

Fhamitha M

2 days ago

0 Stanislav Stilyanov 2 days ago

TI__Mastermind 18970 points

Hi Fhamitha M,

Series resistor is recommended for Clock and Data/Command series resistors are optional as per items 3 and 4 in this guide:

[FAQ] AM625 / AM623 / AM620-Q1 / AM62L / AM64x/ AM243x (ALV) / AM62Ax / AM62D-Q1 / AM62Px Design Recommendations / Commonly Observed Errors during Custom board hardware design – eMMC MEMORY Interface

You may also want to refer to item 9 for the drive strength.

Thanks,

Stan

0 Kallikuppa Sreenivasa 1 day ago in reply to Stanislav Stilyanov

TI__Guru**** 192689 points

Hello Fhamitha,

AM64x implements Hard Macro eMMC PHY and had dedicated function.

Can you confirm you are using the latest IBIS model on TI.com.

Can you share the waveform that you are seeing has reflections.

What is the speed you are considering to use?

The SOC implements internal pulls for the data and CMD signals

The clock is drive by the internal logic after reset.

Pullups and pulldown are optional or not recommended on the eMMC interface signals.

Regards,

Sreenivasa

0 Kallikuppa Sreenivasa 1 day ago in reply to Kallikuppa Sreenivasa

TI__Guru**** 192689 points

Hello Fhamitha,

Fhamitha M said:
I also tried 10 Ω and 22 Ω series termination, and the results matched the expected range. Is it recommended to add an external series termination resistor in this scenario?

It is OK to add a series resistor to control possible signal reflections.

Please share the waveform that has been captured on the load side for review (near to the attached device).

Regards,

Sreenivasa

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AM6442: Termination required for EMMC interface in TMD64EVM