4
\$\begingroup\$

I am using a MAX11060 ADC in a project, I have established SPI communications and am able to read and write registers, however I am unable to get any readings, I believe this is due to the crystal not operating correctly.

This assumption is based on before enabling the oscillator 0V when probed, after enabling the oscillator I see a flat 800mV or so.

To backtrack a bit to fix a screw-up in our board design (wrong footprint) we have manually broken out the package and encased in epoxy (as in I REALLY don't want to re-solder this).

enter image description here

I presume the extra capacitance and/or larger loop area has pushed the crystal out of its operating zone.

Is there any way to measure the load capacitance and then adjust, is this as simple as using a multi-meter to measure between each side of the crystal and ground ad adjust to match the rated value.

enter image description here

Can this be done with the crystal in place.

(Also yes I understand mounted like this the chip will not be able to reach its 16 bit performance, the project has reached a it would be good if it would work at all state)

\$\endgroup\$
12
  • 1
    \$\begingroup\$ Everyone has been here and you have my sypathies. Is the xtal on the shorter leads? What about a using a sig gen to feed into Xin then at least you know where the problem lies if it suddenly begins working. \$\endgroup\$
    – Andy aka
    Commented Oct 20, 2015 at 13:09
  • \$\begingroup\$ How have you determined the xtal isn't running? Do you have an oscilloscope or a frequency counter? \$\endgroup\$
    – Nick Johnson
    Commented Oct 20, 2015 at 13:11
  • \$\begingroup\$ Oscilloscopes, I should have been more clear when I said probe \$\endgroup\$
    – Hugoagogo
    Commented Oct 20, 2015 at 13:11
  • 1
    \$\begingroup\$ +1 for this excellent bodge :-) was it not possible to simply bend over all pins ? Probably not as you then would have done that. \$\endgroup\$
    – Bimpelrekkie
    Commented Oct 20, 2015 at 13:14
  • 1
    \$\begingroup\$ As @FakeMoustache pointed out, it could be conductivity of the glue, as well as instead of just removing the capacitors, try to drop some smaller ones in? While you are waiting on a signal generator if you run out of things to try, you could also create a basic oscillator with some transistors and capacitors... although that is a pain. \$\endgroup\$
    – MadHatter
    Commented Oct 20, 2015 at 16:58

1 Answer 1

Reset to default
1
\$\begingroup\$

what can you do?

  • look for oscillations,
  • check for drive on the driven side of the crystal,

  • inject some signal in the undriven side and check that it comes back inverted on the driven side.

  • test the crystal and capacitors out of circuit.

  • test the chip with a signal from an external oscillator.
\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.