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AM3354: The problem about the GND connection of the crystal circuit.

Kevin Chen81
Intellectual 340 points
Part Number: AM3354

Our customer has designed the AM3354 board according to the reference design. There are some problems during they debugging the board.

1、The GND of the OSC0 and OSC1

On the reference design, the GND of the OSC0 and OSC1 is not connect to PCB Digital Ground directly. I have got the information from the ‘Advisory 1.0.30’. And the best solution is Connect the VSS_OSC and VSS_RTC terminals and respective crystal circuit component grounds directly to the nearest PCB digital ground, making it more difficult for noise to couple into the crystal circuit.

2、is there a internal crystal to use, if we do not use the OSC1(32.768) circuit.

Our customer's design is the same to reference design. And the OSC1(32.768K) does not work well. 

They want to remove the OSC1 circuit. but they are not sure if there is a internal crystal for instead. And how to config the circuit to use the internal crystall.

3、Is the clock of serial port related to OSC1

If we removed the external OSC1 circuit, can the serial port work? How many functions are related to OSC1 and what is it? 

we are looking forward to your help.

 

Thanks and Best Regards!

 Kevin Chen

  • 0
    TI__Guru**** 393215 points
    Hi,

    OSC1 is the 32.768kHz clock source. There is no internal crystal for this clock. There is an internal RC oscillator, but it has a very large deviation (generated clock can be in the range from 10kHz to 60kHz). Another possibility is to source the 32.768kHz clock from the Peripheral PLL. See section 8.1.6.8 in the AM335x TRM Rev. P for details. The 32.768kHz clock is used for RTC, Timer and GPIO debounce. UART's don't use it.