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ADS1014: One shot mode for conversion synchronization

jimmy xu
Prodigy 50 points
Part Number: ADS1014
Other Parts Discussed in Thread: ADS7142
Our application is to monitor laser power. In consideration of signal integrity,  ADC would be located closely with transimpedance amplifier, 
and the data acquisition module will be 12-15 inches away from a microprocessor.
 Several key areas we consider:
1) small footprint of laser monitoring module, 
2) low power, 
3) less wire connection from the module to microprocessor, 
4) ADC conversion sync with laser pulse firing, 
5) Laser pulse firing rate is 50 Hz. 
6) ADC resolution 12 bit is good enough since we have gain stage at transimpedance amplifier.
Do you think ADS1014 would fit our application situation since it has one-shot mode for achieving the conversion synchronization goal?
If not, do you have suggestion for our application case?
Thanks
  • 0
    TI__Guru** 112935 points

    Hi Jimmy,

    Welcome to the E2E forum! The ADS1014 would seem to fit the majority of your criteria.  I guess that the only concern I would have is how closely you need to trigger the conversion relative to the laser firing.  The ADS1014 would require that the conversion be started via I2C configuration so there would be a slight communication lag.  Can you tell me more about the conversion synchronization timing criteria and goals?

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Prodigy 50 points

    Hi Bob,

     With regards to timing criteria of the triggering, there are two areas in our consideration: 1) time latency between the laser firing and ADC conversion, 2) timing variation between every time ADC conversion after receiving the I2C command of "one-shot". For the first one, it is not so critical since a calibration would be applied. for the second one, it is critical since it is directly contributed to our laser monitoring accuracy. How do you think about the time variation of ADC conversion for this chip? 

    Thanks for your time and support.

    Jimmy

  • 0 in reply to jimmy xu
    TI__Guru** 112935 points

    Hi Jimmy,

    There can be some variation of startup to take the conversion over temperature.  Across temperature the internal oscillator can vary by +/-10%.  This will affect both when the conversion begins and the time when conversion completes.

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Prodigy 50 points

    Hi Bob -- I see. The +/-10% variation is not allowed in our application. Our design spec stability spec: ± 2.5% over 24 hours in a temperature range of 15 °C to 45 °C. Do you have some chip could be recommended for our application? Not limited to I2C interface, could be SPI interface.

    Really appreciated your time and help.

    Best Regards,

    Jimmy

  • 0 in reply to jimmy xu
    TI__Guru** 112935 points

    Hi Jimmy,

    Take a look at the ADS7142.

    Best regards,

    Bob B

  • +1 in reply to Bob Benjamin
    Prodigy 50 points

    Hi Bob -- The ADS 7142 you recommended seems good for our application. I plan to buy an EVA board for the test. Thanks for the help. Really appreciated.

    Jimmy