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TRF7962A Won't Clock with Crystal or CMOS Osc

Other Parts Discussed in Thread: TRF7962A

We mounted a TRF7962A on a PCB with a ABM3C-13.560MHZ-D4Y-T crystal. The TRF always output a stable 13MHz waveform on OSC_OUT. Sometimes SYS_CLK started immediately, sometimes it took several seconds, and sometimes it never started. We verified that the TRF always had power, gnd and EN directly on the pins. 

We thought the problem might be the oscillator so we switched to a 13.56MHz 3V CMOS oscillator. It outputs the correct waveform but now SYS_CLK never comes up at all. 

The datasheet says that Pin 31 (OSC_IN) is a "crystal or oscillator input". Is there some issue with connecting a CMOS osc to Pin 31? Has anyone else had these extensive clocking problems?

Thanks

  • Nick -

    To date, none have been reported.

    Do you have a pull-down on EN, EN2 lines being controlled by MCU?

    Are you following the recommended start-up sequence? http://www.ti.com/lit/an/sloa168/sloa168.pdf

    Can you share your schematic?

    Is it possible someone changed your code to write register 0x09 B4&B5 to 0 on startup?

    what are voltages on BG, VDD_X and VIN and VDD_I/O?

  • Hi Josh,

    On the non-functional one: VIN = 5V, VDD_X = 3.5V, VDD_IO = 3.2V & V_BG = 1.5V. I followed start up sequence and padded the timing. I wrote my own PIC32 code which worked fine on TI Demo board. Yesterday I couldn't read the regs at all. 

    Today I replaced the chip and the second one worked fine. Maybe the 1st one had ESD damage.

    Thank you.

  • Nick - glad you got it working, most likely its not ESD damage, these ICs are pretty sturdy - in fact our test engineer was surprised at his inability to damage them when he did his characterization and so forth...so maybe you had a bad solder joint - but if you like we can look at the IC or if you already tossed it - then its a closed issue.

     

  • That's a good idea, but I already tossed it. I did use an Xacto knife to ohm out every pin, but there may have been a problem with the pad underneath. It is tough working with QFNs by hand.

    Thanks for your help. Very nice chip by the way. Does a great job simplifying complex RF for ease of use.