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OMAP3530/DM3730 : MMC3 and level shifter

sebastien72887
Prodigy 100 points
Other Parts Discussed in Thread: DM3730, OMAP3530

We are designing board OMAP3530/DM3730 based.
We want connected to MMC3 1.8V a WI2WI Wifi module SDIO 3.3V with voltage translator.

In BeagleBoard Refernce Manual, it is written :
8.26.2 MMC3 Signals
These signals can be used to provide an additional SD/MMC interface on an expansion
board. All of these signals are 1.8V, so if you plan to use the signals as an SD/MMC
interface, then a level shifter will be required.

But in http://processors.wiki.ti.com/index.php/SD-MMC_Usage_Notes_on_OMAP35x_and_AM37x :
MMC3 operates ONLY at 1.8V and cannot support external voltage translation

Our WI2WI module is SD1.1.
What is the chip reference of level shifter compatible with MMC3 port ?
Does anyone has already connected level shifter to MMC3 ?

Thanks in advance,
Seb

  • 0
    TI__Genius 9190 points

    Hi Seb,

    further down in that wiki page it explains why we recommend not using a level shifter:

    Using MMC3

    It is recommended that MMC3 be only used for 1.8V connectivity devices. It does not have an internal transceiver like MMC1 and does not have external direction signals like MMC2. It is possible to put auto direction sensing transceivers as described with MMC1, however, the buffer strength and loading constraints are restricted with MMC3. Typical buffer strengths for MMC3 is 4mA vs. 8mA for MMC1. Also, MMC1 can handle up to a 30pF load, whereas MMC3 can only handle up to 14pF load.