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AM3351: OSC1 fails

Biren Salunke
Prodigy 80 points
Part Number: AM3351

Hi,

On one of the new design with octavo SiP OSD335x which uses AM335x processor, OSC1 32.768 kHz crystal is not oscillating, IN is staying logic high and OUT is low. We are using ECS-.327-12.5-1210-TR crystal which has 12.5pF load capacitance and ESR of 90k. We tried different crystal ABS06-107-32.768KHZ-T which has 4pf load cap and 60k ESR but same behavior.

AM335x spec call out for 80k max ESR as per table 6-5. 

We tried different values of capacitors 12, 15,18, 22pF and try to clean area very well after each rework but didn't help. We don't have optional resistors in the design as per datasheet. 

Does anyone has experienced issue like this issue? All voltage rails looks stable. 

Thanks,



  • 0
    TI__Guru**** 393215 points

    Hi,

    OSC1 is disabled by default after power is applied. This clock input is optional and may not be required if the RTC is configured to receive a clock from the internal 32k RC oscillator (CLK_RC32K) or peripheral PLL (CLK_32KHZ) which receives a reference clock from the OSC0 input. See section 6.2.1 from the AM335x Datasheet Rev. L.