PGA300: PGA300 DAC Calibration

Hi Ed,

Are these tests all being conducted using the PGA300EVM? Does the low current output occur only with the calibrated output? First, please test that the full current range is available by manually commanding the DAC. You should be able to achieve around 30mA with the max DAC code (0x3FFF).

Please also check that the clamping values are not set in such a way that interferes with your desired normal operation range. (The NORMAL_HIGH/LOW and HIGH/LOW_CLAMP EEPROM registers).

Regards,

Hello Scott,

These test was conducted using the PGA300EVM. Please see snapshot below, I made this snapshot when 300EVM was offline, there should be value in  "calc DCA (Hex)" column, it happened during "DAC Code Calculation", when click on "Write DAC Code" with 20mA, sometime it was 15.xxx mA, sometime it was even 5.xxx mA, it might be 19.9xx mA next day.

Please help, thanks.

Ed

If the DAC code you are writing is the same, the current output should be relatively consistent. What kind of load do you have on the output?

Regards,

Hello Scott,

When I highlight "DAC Codes HEX" - 2700, click on "Write DAC Code", then Amp meter should show value around 20.00mA, unfortunately it shown 16.xx mA, even 5.xx mA, I set up loop for "PGA300 - 24VDC - Current Metter" for all systems, only this one has problem.

Thanks.

Ed.

Hi Ed,

Do you mean that only one board shows this issue? Or that only when setting the DAC output to 2700h you see an unexpected current on every one of your boards?

Regards,

HI Scott,

EVERY ONE of my boards. It happened recently, if I restart OWI, some boards could get 20.000mA around reading, some of them never make it. Thanks.

Ed

Hi Ed,

Can you please send a picture of your EVM or describe all of the jumper settings on your board? This seems to me like the DAC is trying to supply more current than it is capable of, and it's causing the voltage to drop. That will make it tough to the drive the BJT properly for the current loop control.

Regards,

I cannot publish picture in this new "sensors forum", could you please provide email address?

Hi Ed,

The new image publishing feature is under "Insert->Image/Video/File." When the popup comes up you can click on the upload button to open the browser to select the picture. You can also add me as a friend on E2E and you can send it through the messages there.

Regards,