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PGA302: Bridge acquisition

Stefano Zanotti
Prodigy 70 points
Part Number: PGA302
Other Parts Discussed in Thread: TL071

Hello,
we need to acquire data from a 3-axis accelerometer and 3-axis angular rate sensor.
Each channel is a bridge, and we thought of using your PGA302 device, or a similar one.
However, our sensors need an excitation of 3mA (accelerometers) and 6mA (angular rate sensors), which is more than the 1mA stated in the PGA302 datasheet.

Also, we would like to read the data through a digital interface (SPI, I2C, etc.). Only if the digital interface is not fast enough, we would sample the DAC output of the device.
Since we need a sampling frequency of 20kHz (this is the bare minimum, a higher frequency would be preferable if possible), it seems like I2C is not fast enough (at least at a standard 100kHz speed).

Do you have other devices in the PGA302 family to meet our needs?
Or other devices for bridge acquisition?

Regards

P.S. The sensor we need to acquire is this: www.thp-systems.com/.../DTS-DatasheetDTS6DX-PRO_DSH-003.pdf

  • 0
    TI__Mastermind 31655 points
    Hi Stefano,

    In order to supply higher current levels to the bridge inputs, you can use an externally supplied buffer off of the bridge excitation. You could use something as simple as the TL071.

    The PGA302 uses a delta-sigma ADC which oversamples at 4Mhz, but it outputs at 96us (~10kHz), so that is the fastest that you will be able to get data from the device regardless of the communication method.

    What are your requirements, so that I can better help you pick a suitable device? From your message you need >20khz sampling rate, digital interface for output, 2 channels, and some sort of bridge excitation supply. What resolution do you need? Any other requirements?

    Thanks,
  • 0 in reply to Scott Cummins
    Prodigy 70 points
    Hi Scott,
    thanks for your reply.
    We need to read 6 channels (3 accelerometers and 3 angular rate sensors).
    Ideally we would have 16 bits of resolution, though we could settle on 14 (like the PGA302 DAC output).
    Bandwith is >20kHz (we'd like 50kHz, but can settle on a lower value if necessary).
    Both a sigma-delta or a SAR architecture would do.
    Digital interface is preferred over analog (and SPI is preferred over I2C), but this secondary to the bandwidth and resolution.