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PGA309: issues calibrating the PGA309 with a USB-DAQ board

Amy Luo
Expert 6895 points
Part Number: PGA309

Hi team,

Here are some of the issues one of our customers is experiencing, could you please provide some troubleshooting advice?

I'm calibrating the PGA309 with a USB-DAQ board and I'm experiencing two problems

1. The output of PGA309 is 0.5-4.5V analog output, but when I use register R5 for clamping, the lower clamp can reach 0.21V or so. But the upper clamp only goes up to about 4.04V. The range I want to use is 4.5V, and the upper clamp should be greater than the 4.5V operating value. For example, if VREF is 4.096V and R5 is set to HEX47, the output will have a lower clamp of 0.21V and an upper clamp of 4.02V. 

2. Now with two USB-DAQ boards respectively set the jumper cap address 2F90, 2F91, parallel operation will appear 2F90 read and write no problem but 2F91 read and write will often unsuccessful situation, I made a copy of the Tio32.dll folder and renamed it for the use of the 2F91 thread.

I am looking forward to your reply! Attached are the EEPROM values for some products

EEPROM.txt 
5449_0000_0103_0597_D31F_007F_1703_BA7B_2941_4B79_99FF_2941_0000_0000_2941_0000_0000_2941_0000_0000_2941_0000_0000_2941_0000_0000_2941_0000_0000_2941_0000_0000_2941_0000_0000_2941_0000_0000_2941_0000_0000_2941_0000_0000_2941_0000_0000_2941_0000_0000_2941_0000_0000_2941_0000_0000_2941_0000_0000_7FFF_0000_DD37
5449_0000_0103_0594_C41F_0047_1703_C9B6_2932_6801_8ED3_2932_0000_0000_2932_0000_0000_2932_0000_0000_2932_0000_0000_2932_0000_0000_2932_0000_0000_2932_0000_0000_2932_0000_0000_2932_0000_0000_2932_0000_0000_2932_0000_0000_2932_0000_0000_2932_0000_0000_2932_0000_0000_2932_0000_0000_2932_0000_0000_7FFF_0000_CCDA

Tio332_240125_145719.log

Best Regards,

Amy Luo

  • 0
    TI__Mastermind 22277 points

    Amy,

    1. The PGA309 over and under scale limit is designed to be a ratio of the reference voltage Vref (see user's guide PGA309 user's guide section 2.9).  Thus, if a 4.096V reference is used the maximum clamp is 4.096V * 0.9708 = 3.976V.  If a 5V external reference is used the clamp can be 5V * 0.9708 = 4.85V.  I believe that this feature was mainly intended for use with an ADC where the ADC reference is shared with the PGA309 reference.  This way the PGA309 output never exceeds the ADC reference voltage.  If you want a clamp that allows for 0.5V to 4.5V you will need to use an external reference.
    2. I do not believe that the PGA309EVM software allows for two EVM to be run at the same time.  The address select option is used to select the USB HID product ID.  The software automatically scans the four available product ID to see if one is present, and will attempt communications if it finds one.  I am not sure I understand your question.  Are you successfully communicating with two devices at once?  I suggest if you want to calibrate multiple sensors at once you use the MULTI-CAL-SYSTEM 

    I hope this helps.  Best regards, Art Kay

  • 0 in reply to Art Kay
    TI__Expert 6895 points

    Hi Art.

    Thank you for your assistance. Below is the follow-up question from this customer, could you please give your comments.

    1. regarding the clamp being located on the internal reference, I reviewed the information in your guide and my understanding is that to achieve the operating conditions I need (other than 0.5-4.5V) I need to make a change to the product (the PGA309 sensor) and I need to connect the 5V from the VS to the 12PIN of the 309 and set D10D8 in R3 to zero.

    2. When calibrating the 309 on two USB-DAQ boards in parallel, I developed a software to do this using TIO32.DLL provided by TI, and this has caused some problems during the work, and just yesterday I reconnected JUMP8 on one of the boards to GND, and found that the problem has magically improved a lot, and I don't understand what is going on here, and I looked at the manual for information that JUMP8 is a One-Wire accelerated circuit, and that it is a one-wire accelerated circuit. I read in the manual that JUMP8 is a One-Wire accelerated circuit and it was connected to SPD when I had the problem before. Also, I would like to ask if I have to enable the acceleration circuit if I add a 100pF capacitor to the OUT pin in 3-wire mode?

    Again, I look forward to your reply!

    Thanks,

    Amy

  • +1 in reply to Amy Luo
    TI__Mastermind 22277 points

    Amy,

    1. You will need to connect pin 16 on the PGA309 (Vref) to 5V.  One option is to connect Vs (Pin 3) to Vref (pin 16).  However, Vs is often has drift an noise when compared to a precision voltage reference.  This may be ok if you are doing a ratiometric design.  That is, the voltage reference connected to the PGA309 is also connected to the ADC that is reading the PGA309 output.  Using the ratiometric approach, when the reference shifts the PGA output will shift by the same percentage, and the ADC input range (LSB size) will also shift by the same percentage.  Thus the shift will cancel out.  On the other hand, if you expect the output to have absolute accuracy, you should use an external 5V voltage reference on pin 16. 
      1. I do not understand your comment regarding "D10D8 in R3 to zero."  I do not see this component on the PGA309EVM test board.
      2. Your comment regarding pin 12 of the PGA309 does not seem correct.  This is the PRG pin and is used for digital communications.  It would not make sense to connect Vs directly to the PRG pin.
    2. The "one-wire speed up circuit" JUMP8 is generally recommended to be turned on for all PGA309 operation.  In fact, I do not believe I have every used this in the off position.  It is especially important to use this when long cables are used.  The purpose of the circuit is to add a current boost on the one-wire digital signal to make the rise time faster.  This reduces the possibility of data communications issues from slow rise time.  The circuit works effectively on the EVM to drive a 10nF capacitor so you should not have issues with 100pF.

    I hope this information is useful for you.  Best regards, Art

  • 0 in reply to Art Kay
    TI__Expert 6895 points

    Thank you Art.