This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

PGA309: OWD bit

Part Number: PGA309

Hi, 

In the user's guide I read :

"In four-wire module applications, it is essential that the OWD Bit (Register 4 [D15]) be set to '1' to disable the One-Wire interface after final programming is complete and before the final sensor module is sent out to the end application."

I already use a Pull-up on the PRG pin. Should I set this OWD bit to "1" in this case ? Because when I set OWD to "1" after calibration the sensor doesn't work (maybe due to this pull up)

Do you have some pieces of information ?

Thx

Guillaume

  • HI Guillaume,

    Most users will disable the one-wire interface (OWD=1) in four-wire applications after the final EEPROM program write after performing calibration.  Setting OWD='1' helps prevent periodic noise causing issues with the PGA309 or EEPROM programming after calibration has been performed.

    Setting the OWD to "1" disables the one-wire interface after 25-ms after power-up. When OWD is set to ‘1’ (Register 4, bit D15), the time interval after power-up is the only opportunity that an external communications controller can initiate digital communication with the PGA309 one-wire interface and trigger a one second delay in the internal state machine.   If OWD is set to ‘1’, after a initial POR is completed, and a valid Checksum2 is received, the One-Wire interface will be disabled after a 25-ms delay, and the PRG pin becomes high impedance, and One-Wire communication cannot take place unless power is cycled.

    The OWD is discussed on a few sections of the PGA309 User Guide:

    - Section 3.1 "Power-On Sequence and Normal Stand Alone Operation" on page 60 of the user guide,

    - Section 4.8, "PGA309 Stand-Alone Mode and Two-Wire Transactions", on page 83, 

    - Section 4.10 "One-Wire Operation with PRG Connected to VOUT" page 88, and figure 4-16 page 90.

    - Section 4.11,  "Four-Wire Modules and One-Wire Interface (PRG)" page 91.


    Settling OWD=1 disables communication after a delay and then the PRG pin becomes high impedance. 

    If the device has been already calibrated, I can't immediately think of a reason why the sensor calibration wouldn't work.   Do you have a detailed description of the issue that occurs after enabling OWD='1"? 

    Thank you and Regards,

    Luis

  • Hi Luis,

    All is explain in the word file :

    detailed issue.docx

    Thx

    Guillaume

  • HI Guillaume,

    I performed a few experiments using the PGA309EVM-USB.  I used both of your EEPROM files with OWD=0 and OWD=1 with your calibration settings using an external sensor injecting a small 0mV-5mV differential signal at 2.5V common-mode.  In addition, I also performed other experiments with default EVM models using the Auto Cal feature with the built-in Sensor emulator on the EVM and  experimented setting OWD=0 and OWD=1 on the EEPROM with similar results.

    - When using your settings with an external  precision sensor emulator, loading your exact EEPROM settings with OWD=0, cycling the VS power supply and setting the test pin low, the device powers up properly, where the output of the PGA309 follows the input signal.  Using the block diagram, and setting test pin high, the EVM allows to change register settings without issues and is able to read register settings as expected.  

    - When using your settings with an external  precision sensor emulator, loading your exact EEPROM settings with OWD=1, cycling the VS power supply with the test pin low, the device powers up properly, where the output of the PGA309 follows the input signal with the expected gain settings.  In this case, after resetting VS power with Test pin low, with the EEPROM programmed to OWD=1, toggling then Test Pin High on the block diagram, does not have an effect on the PGA309 output, the PGA309 still works gaining up the input signal as expected.  However, the GUI appears to not be able to communicate register settings since the PRG pin communication is disabled. In other to re-establish communication, I need to re-program the EEPROM with OWD=0, or alternatively, power up with test pin high and re-program registers settings.

    The calibration settings are not lost, but as expected, the PGA309 powers up with the programmed settings and produces the expected output signal proportional to the sensor input.  However, after cycling power with EEPROM programmed to OWD=1 and test pin low, the EVM GUI appears to no longer able to communicate register settings. In order to re-establish communication, power can be cycled with test pin high (powering up with test pin high disables EEPROM communication at power up) and resets device to POR settings,  and then the register settings can be re-programmed.   Alternatively, the EEPROM can be re-programmed with OWD=0.  

    Thanks and Regards,

    Luis

    OWD=0 settings:

    OWD=1 settings:

        

     

  • Hi,

    I found what was the problem ! :

    To program my pressure sensor I use the USB DAQ EVM connected to my sensor with 1.5m cable... (5 wires : GND, PROG, TEST, SCK, SDA to be able to use both kind of communication)
    After changing OWD = 1 and Switching power ON-OFF-ON, The sensor didn't work because the lengh of the wires on the SCK and SDA acts as an antena (I think), makes data mistakes between the PGA and the memory.
    And If I disconnect the cable close to the USB DAQ EVM the problem is the same because the SCK and SDA are connected to 1.5m of wire.
    But if I disconnect the cable close to the sensor,no antena, no problem, the sensor works well.

    Guillaume

  • HI Guillaume,

    Many Thanks for letting us know, and providing the detailed information.   It is always helpful for future reference.

    Glad you were able to resolve the issue,

    Kind Regards,

    Luis