Question, i.MX21 EXT_48M, EXT_266M

[Aemj]

Dear team,

I would like to ask about schematic design for i.MX21 board.

My customer is using i.MX21 for their product.

Recently, they found i.MX21 on the board could hang in a certain circumstance.

And they found the following pins are left open on the board though i.MX21 datasheet says those pins should be connected to GND.

- EXT_48M, EXT_266M

They need to know whether those pins left open are cause of this issue.

Could you show me what phenomenon can happen in the case that those pins are left open?

BTW, the parts# is MC9328MX21CJM.

Thanks,

Miyamoto

[art · Accepted solution]

The EXT_48M and EXT_266M pins are meant for factory testing purposes only and must be connected to GND for regular operation. These pins are meant for PLL-

bypass testing of the chip's on-die clocks, so, their improper connection may prevent the internal clocks from running continuously during normal operation, and, therefore, lead to the hang-up of the whole chip. Please ask the customer to connect these pins to GND during normal operation. Otherwise, the stable operation of the chip cannot be guaranteed.

Have a great day,
Artur

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