PGA309EVM-USB: Test mode, EEPROM configuration, manual vs automatic calibration

Felix Debus

Part Number: PGA309EVM-USB
Other Parts Discussed in Thread: PGA309

Tool/software:

Hi team,

we want to calibrate the offset of a bridge with the PGA309 and we have some questions here.

For testing we use the PGA309EVM and the PGA309 GUI. To test the calibration we switched from the EEPROM configuration to the test mode. I already went through a couple of e2e posts but could not find a solution so far. If I have overseen them please let me know.

1. We observe that if we change a value in the tab 'Block Diagram' of the GUI the value is overwritten after a 'Read all Reg' was performed. Please note that we already changed into the test mode. Why does it overwrite the value?

2. Alternatively we think about changing the EEPROM configuration. For clarification: In the GUI a 'Load EEPROM With File' option is given. This does not write data in the EEPROM instead this writes the EEPROM data into the device's registers? I found the e2e post PGA309EVM-USB: Load EEPROM with file. To program the EEPROM they would need to follow the steps mentioned in PAG309 problem with EEPROM?

3. Can you please help me to understand what is the difference between the manual and automatic calibration? Are there limitations of the automatic calibration?

Can you please help us with our questions?

Best regards

Felix

2 months ago

+1 Caro Walter 2 months ago

TI__Mastermind 22172 points

Hello Felix,

Apologies for the delay in response, there was a US Holiday.

Felix Debus said:
1. We observe that if we change a value in the tab 'Block Diagram' of the GUI the value is overwritten after a 'Read all Reg' was performed. Please note that we already changed into the test mode. Why does it overwrite the value?

With the Test Pin ON, if the value is changed from the block diagram, 'Write All Reg' to save value, 'Read all Reg' to see output changed.
If the value is changed from the block diagram and 'Read all Reg' is selected, without 'Writing All Reg' to save the value, the previous value is written.

I have attached a ppt that shows this more clearly as it required several images: PGA309EVM GUI.pptx

Felix Debus said:
2. Alternatively we think about changing the EEPROM configuration. For clarification: In the GUI a 'Load EEPROM With File' option is given. This does not write data in the EEPROM instead this writes the EEPROM data into the device's registers? I found the e2e post PGA309EVM-USB: Load EEPROM with file. To program the EEPROM they would need to follow the steps mentioned in PAG309 problem with EEPROM?

To load the registers and block diagram from the EEPROM, I recommend the following procedure:

Block Diagram tab: Test Pin ON
EEPROM tab: Load EEPROM with File
Block Diagram tab:
1. Test Pin OFF
2. Read all Reg
3. Block Diagram and Registers tab will both update

3. Can you please help me to understand what is the difference between the manual and automatic calibration? Are there limitations of the automatic calibration?

In the Auto-cal tab, the difference between Manual calibration (clicking 'Start' and 'Continue' a lot of times) and automatic calibration (pressing auto-continue) is that manual allows you to time to change the pressure and temperature in the calibration routine - these are guided by the dialogue box at the top of the screen, here are a couple of examples:

Once all manual calibration is complete, the user is prompted to write to EEPROM.

Auto-continue is usually used the sensor emulator that does not require the user to change the pressure or temperature as these are being emulated & aren't an actual pressure sensor in a temperature range. The calibration results are written into the EEPROM, and the program will not stop until "Calibration Complete!"

I recommend setting up the calibration in "Set up Cal" tab and running the calibration in "Auto-Cal," this is the easiest way to use the device.

All the best,
Carolina

0 Felix Debus 2 months ago in reply to Caro Walter

TI__Intellectual 980 points

Hi Carolina,

thank you for your answer!

Regarding point 1 the value was also overwritten with previously saved the values via the Write All Reg button. Is there an option in the GUI where some values can not be written if they are ouf range for example?

Best regards

Felix

0 Caro Walter 2 months ago in reply to Felix Debus

TI__Mastermind 22172 points

Hi Felix,

I was looking at "Zero DAC" when comparing, what values are you following?

All the best,
Carolina

0 Felix Debus 2 months ago in reply to Caro Walter

TI__Intellectual 980 points

Hi Carolina,

thank you it works now!

We have now another question.

Can we 'read' in the voltage offset from the application with the PGA309EVM and if yes how do we need to consider the value to the calculation to compensate it? Is it done with the automatic calibration?

Best regards

Felix

0 Caro Walter 2 months ago in reply to Felix Debus

TI__Mastermind 22172 points

Hi Felix,

The PGA309EVM does read the sensor min and max in order to determine the correct gain options to calibrate the desired output. The PGA309EVM does not characterize the sensor for the customer.

Instead, the customer will have ideally already measured their sensor and/or has the sensor's datasheet. From there a sensor emulator model may be created from the "Set up Cal" file, below is an example off of a sensor's datasheet:

Once the sensor has been emulated correctly, in the Auto-cal tab, the PGA309EVM will run through the calibration routine to determine from sensor measurements what internal registers must be set to provide the expected output voltage.

All the best,
Carolina

0 Felix Debus 2 months ago in reply to Caro Walter

TI__Intellectual 980 points

Hi Carolina,

thank you, we will let you know how it worked!

Can you please help us to understand another topic regarding the PGA309?

Attached you can find a setting our customer had done.

If we would had for example 2mV offset we would set the coarse offset to -3.48mV which would result in -1.48mV.

This is value is then multiplied with the gain of 128. The output then is still positive. Can you please help us to understand if there is a calculation for the output of the first OPA?

From your point of view, what would be the best way to compensate an ofset value which is in between the steps of the coarse value? Would the Set up cal functionality solve this?

Best regards

Felix

0 Caro Walter 2 months ago in reply to Felix Debus

TI__Mastermind 22172 points

Hi Felix,

The calibration routine will automatically solve this for the customer. The calibration procedure is outlined in Section 5.4 of the User's Guide.

The coarse offset isn't calculated until Step 7, please have the customer follow these steps if they would like to calculate coarse offset - however my recommendation is to just connect the EVM and run through a calibration routine instead.

All the best,
Carolina