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PGA309: EEPROM interface

Ankeet Gugale
Prodigy 155 points

Part Number: PGA309
Other Parts Discussed in Thread: XTR117,

Hello,

We are designing a sensor board for conductivity measurement using Wheatstone's Bridge. We plan to use PGA309 and XTR117 for converting voltage to current loop.

We found one application note (slau526- Digitally Calibrated Bridge Sensor Signal Conditioner with 4mA to 20mA Current Loop Output) which we are referring.

Following are my queries:- 

1) How does the EEPROM (interfaced with PGA309) store calibration settings? How to write/ read into the EEPROM? There is no Microcontroller on this board.

2) The circuit diagram in slau526 (page 27) show PRG pin of the PGA309 is connected to 1W. and further the 1W is brought on JUMPER. can you please provide more details as to why this provision is made and whether is it mandatory to connect it the way it is connected or we can leave it open (or connect to VOUT as suggested in some TI documents).

Thanks in advance.

Ankeet Gugale.

 

  • 0
    TI__Guru 55466 points

    Hello Ankeet,

    The PGA309 User Guide (link at the bottom) documents the operation of the PGA309 in good detail.  In addition, the PGA309EVM-USB can help you get started with the PGA309.

    1)  There are two digital interfaces on the PGA309:

    -The PRG pin is a One-Wire, UART-compatible interface, with bit rates up to 38.4kbits/s (38400 baud).

    -The SDA and SCL pins together form an industry standard Two-Wire interface at clock rates up to 400kHz. The external EEPROM uses the Two-Wire interface for programming and reading.

    Communication to the PGA309 internal registers can be conducted through either digital interface, One-Wire or Two-Wire. Additionally, the external EEPROM can be programmed either through the PGA309 One-Wire interface pin, PRG, or by direct connection to the SDA and SCL lines of the Two-Wire interface. Lastly, The PGA309 can write and read to the EEPROM during the calibration process.

    Please refer to the PGA309 user guide for detailed information on page 74-91, Appendix A1, etc.

    2)  The PRG pin can also be connected to VOUT for a three-lead (Vs, GND, VOUT) digitally-programmable sensor.  In this mode, the PGA309 output may be enabled for a set time period and then disabled again to allow sharing of the PRG pin with the VOUT connection.  This allow for digital calibration and analog readback during sensor calibration in a three wire sensor module.  Please review page 16 of the PGA309 datasheet and/or Section 4.10 of the PGA309 User Guide.

    PGA309 User Guide:

    http://www.ti.com/lit/ug/sbou024b/sbou024b.pdf

    PGA309 Datasheet:

    http://www.ti.com/lit/ds/symlink/pga309.pdf

    Thank you and Regards,

    Luis