getting consistent output from ADIS 16375

Hi,

I am trying to get data reading from ADIS 16375 through SPI and I was able to detect output (product ID) only once on scope. I have verified that SPI signals from microcontroller are right. I am using lab power supply to power the device. IMU is only drawing 0.01A and there is some pulse signal on DIO1. I am not sure why IMU is not giving output consistently.

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    •  Analog Employees 
    on Feb 22, 2014 10:58 PM

    How are things going?  We have had to delay our FAQ on a linear regulator design for the ADIS16375, but I wanted to offer some starting points, in case you are going to do this yourself:

    1. ADP3339 or ADP1741 offer sufficient load transient response and peak current capacity
    2. Soft-start function on the ADP1741 might enable you to manage load transients while charging local capacitance.
    3. ADIS16375 has ~24uF of capacitance across power and ground pins.
    4. You might want to consider a large input capacitance for the linear regulator. If you supply 3.6V to the input of the linear regulator, you will want to manage the voltage drop (from the 1.5A surge) to less than 100mV to manage against the regulator's drop-out voltage requirement.
      1. i = C * dv/dt
      2. C = i * dt/dv
      3. Assume an average of 750mA for 200us
      4. C >= (0.75 x 200us)/(0.1V) >= 1500uF
      5. This calculation assumes a number of "worst-case" things that may not reflect reality. For example, the lab supply will likely provide some support; this computation assumes that the local capacitor will have to supply it all.
    5. You can limit in-rush current from your lab supply by using its current limit. Verification is a good idea but our lab supplies provide constant current while charging load capacitors and remain stable as they approach the final target.  If you do this, you will want to make sure that the VDD transients do not exceed the Absolute Maximum the ADIS16375 datasheet.

    I hope that this helps!

    Best,

    NevadaMark

Reply
  • 0
    •  Analog Employees 
    on Feb 22, 2014 10:58 PM

    How are things going?  We have had to delay our FAQ on a linear regulator design for the ADIS16375, but I wanted to offer some starting points, in case you are going to do this yourself:

    1. ADP3339 or ADP1741 offer sufficient load transient response and peak current capacity
    2. Soft-start function on the ADP1741 might enable you to manage load transients while charging local capacitance.
    3. ADIS16375 has ~24uF of capacitance across power and ground pins.
    4. You might want to consider a large input capacitance for the linear regulator. If you supply 3.6V to the input of the linear regulator, you will want to manage the voltage drop (from the 1.5A surge) to less than 100mV to manage against the regulator's drop-out voltage requirement.
      1. i = C * dv/dt
      2. C = i * dt/dv
      3. Assume an average of 750mA for 200us
      4. C >= (0.75 x 200us)/(0.1V) >= 1500uF
      5. This calculation assumes a number of "worst-case" things that may not reflect reality. For example, the lab supply will likely provide some support; this computation assumes that the local capacitor will have to supply it all.
    5. You can limit in-rush current from your lab supply by using its current limit. Verification is a good idea but our lab supplies provide constant current while charging load capacitors and remain stable as they approach the final target.  If you do this, you will want to make sure that the VDD transients do not exceed the Absolute Maximum the ADIS16375 datasheet.

    I hope that this helps!

    Best,

    NevadaMark

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