TUSB8041: If not R1 resistor(1Mohm) on Crystal circuit, What happen?

Hi JMMN-san,

Thank you for your response.

I understand it.

let me confirm one.

Is there internal resistor in parallel to the crystal?

Because crystal vender said to customer that the resistor is needed for correct operation, but it works without R1 1M ohm resistor external. So they would like to confirm whether there is internal resistor.

Best regards,

Katsu

Hi JMMN-san,

Crystal vender says that the resistor in parallel is needed, but customer's board is working without the resistor.

Could you please give any comment why the customer board works on their board?

Thanks and best regards,

Katsu

Hello Katsu,

I will check on the internal circuit.

Regards,

JMMN

Can you share the crystal datasheet?

Thanks,

JMMN

Hi JMMN-san,

You can see the datasheet here.

https://www5.epsondevice.com/en/products/crystal_unit/fa238.html

Part number is below

FA-238 24.000000 MHz 12.0 +30.0-30.0

Thanks and best regards,

Katsu

To check whether there is a built-in feedback resistor, measure the XI/XO voltage on a powered device while nothing else is connected to these pins. If the resistor is present, it's V_CC/2, otherwise, V_CC or GND.