i.mx8M Plus Pin function of AD28

[Melshia]

Hi NXP Team,

We are designing a Hardware platform using the MIMX8ML6NKZACVB Processor. We are planning to use the AD28 Soc pin for the power enable function of the SD card. This power enable (PWR_EN) signal has to be maintained at 1.8V and connected at the B2B Connector.

From the Confiq tool, this pin AD28 has 2 alternate functions, like USDCH2_RESET & GPIO. Please confirm which function I need to consider this AD28 pin for the Power Enable (PWR_EN) Function in my design

I have checked this pin, AD28, in the i.mx8M plus reference schematics document SCH-46368, and found that the signal SD2_RESET_B is connected to the PCA9450 (PMIC) SW_EN pin.

1. Please confirm this pin acts as USDCH2 or GPIO in EVK.

2. Please confirm in EVK Schematics NVCC_SD2 is powered at 3.3V or 1.8V

[yipingwang]

I discussed with the AE team, please refer to the following update.

On the NXP EVK board, ball AD28 is assigned as SD2_RESET_B to control the load switch inside PCA9450C for SD card connected to SD2 IF. This setting is enabled by the ROM code and Linux BSP to support SD 3.0 well.

To make it work correctly, SD2_RESET_B shall be pulled up to NVCC_SD2 with 4.7KOhms resistor.

 

To support SD 3.0, NVCC_SD2 is set as 3.3V out of reset and will be set as 1.8V to support high speed access. That means SD2_RESET_B signal level is switched between 3.3V and 1.8V also.

Customers can use the load switch inside PCA9450C by connecting VSD_3V3 to the B2B connector with 2 or more pins for cost-down.

If customers want to use external load switch on the base board instead, it can be enabled with SD2_RESET_B (so called as PWR_EN) which has been pulled up to NVCC_SD2 with 4.7KOhms resistor on the CPU board. Please just connect SD2_RESET_B together with the left signals of SD2 IF to the B2B connector.

[Melshia]

Hello NXP Team,

Thanks for the reply.

We are planning to use the External Load switch on the Base Board.

Please confirm this PIN AD28 when working for the PWR_EN signal, it will be under the USDCH2 bank, so can I directly connect this signal to the B2B Connector to enable the load switch in the Base Board?

[yipingwang]

Yes. It would be fine if the external load switch can be enabled by 1.8V level signal.

[Melshia]

Hello NXP Team,

Thanks for you reply.

We will provide the PWR_EN signal connection from the AD28 Pin directly to the B2B Connector.