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LDC1000-Q1 - oscillator issue

Varban Metodiev
Intellectual 690 points

Hello Team,

Recently I have been trying to get the LDC1000-Q1 working.

As it is in IC the documentation, we have connected an 8Mhz crystal across pin 14 (TBCLK/XIN) and pin 15 (XOUT). There are also two 20pF capacitors from pin 14 to GND and from pin 15 to GND.

The digital and analog grounds connected (shorted).

LDO bypass capacitor (on pin 13 - CLDO) was added.

The power supply voltage and ground are OK, several 8Mhz crystals have been replaced, tried with another LDC1000 chip, a 8Mhz ECLK pin from TMS570 was also tried out (instead of a crystal)... and the LDC1000 is not working at all. On the oscilloscope - nothing appears even on the crystal pins (pins 14 and 15 on the IC).

Please advise us what to do!

Kind regards,

Varban 

  • 0
    TI__Genius 13650 points
    Hello Varban,
    please check the status of the following registers which could prevent oscillator operation:
    0x05 [bit 0] (CLK_PD, should be 0 in your application)
    0x05 [bit 1] (CLK_SEL, should be 1 in your application)
    0x0B [bit 0] (PWR_MODE, should be 1 in your application)
  • 0 in reply to Ben Kasemsadeh
    Intellectual 690 points

    Hello Ben,

    I have tried out all the combinations in the 0x05 register. The proper value should be 0x02h (10b) for the external crystal:

    (BIT1) CLK_SEL: 1:External crystal used for frequency counter (XIN or XOUT).

    (BIT0) CLK_PD: 0:Enable External time base clock

    Also, this was the only one that provided voltage amplitude on the pins. However, the crystal does not start oscillating. The two capacitors (XIN-to-GND and XOUT-to-GND) are chosen as per the documentation.

    The only way I made LDC1000-Q1 working was using a microcontoller pin clocked at 8MHz  and 0x01 value for the 0x05 register.

    Regards,

    Varban