ADS1298RECGFE-PDK: ADS1298R

Saloni Gandhi

Intellectual 260 points

Part Number: ADS1298RECGFE-PDK
Other Parts Discussed in Thread: ADS1298R

I am trying to implement Internal Calibration of ADS1298R.

for that i have configured input it as Test Signal and checking the values at different gain settings.

Test signal amplitude =1 × –(VREFP – VREFN) / 2400 V

so we are configuring Vref as 2.4 v so ans is 2 mV.

It is the correct procedure to check Calibration or not?

over 6 years ago

0 Ryan Andrews over 6 years ago

TI__Guru 59876 points

Hi Saloni,

Thanks for your post.

Remember that the test signal is internally connected to the input of the PGA gain stage. Therefore, the amplitude of the square wave at the ADC output will be the nominal amplitude times the gain. The nominal amplitude is either 1 mVp or 2 mVp, depending on the CONFIG2[2] setting.

Best Regards,

0 Saloni Gandhi over 6 years ago in reply to Ryan Andrews

Intellectual 260 points

My Config2 setting is 0X10 and I am getting

2 mV. So it is correct or not?

0 Saloni Gandhi over 6 years ago in reply to Saloni Gandhi

Intellectual 260 points

for vref as 2.4 volt i have configured config 2 as 0x10 but still it is coming 2 mV.

It should be 2 mV OR 1 mV???

Please reply as soon as possible.

0 Ryan Andrews over 6 years ago in reply to Saloni Gandhi

TI__Guru 59876 points

Hi Saloni,

Are you measuring the peak amplitude or the peak-to-peak amplitude? For Gain = 1, the test signal should measure 1mVp (2mVpp).

Best Regards,

0 Saloni Gandhi over 6 years ago in reply to Ryan Andrews

Intellectual 260 points

I am measuring peak to peak amplitude, which is 2mV

0 Saloni Gandhi over 6 years ago in reply to Saloni Gandhi

Intellectual 260 points

So it is correct or not?
& for all gain settings it is coming 2 mV only.

0 Saloni Gandhi over 6 years ago in reply to Saloni Gandhi

Intellectual 260 points

I have one more doubt that it is -1 to 1 mV of signal not 0 to 2 mV???

0 Ryan Andrews over 6 years ago in reply to Saloni Gandhi

TI__Guru 59876 points

Hi Saloni,

2mVpp is correct for Gain = 1. That is -1mV to +1mV, since we are only looking at the differential voltage, not the common-mode.

How are you converting from ADC codes to volts? If your equation includes the gain term, then your results are input-referred already. The equation "1 LSB = [2*VREF / Gain / 2^n codes]" calculates the change in voltage at the PGA inputs needed to increase the ADC output by one code.

Best Regards,

0 Saloni Gandhi over 6 years ago in reply to Ryan Andrews

Intellectual 260 points

we are using this equation this equation: ((vref/gain) / full scale value ) to normalized data at every gain settings. That's why we are getting 1 mV every time.
Is that correct????

0 Ryan Andrews over 6 years ago in reply to Saloni Gandhi

TI__Guru 59876 points

Yes.

0 Saloni Gandhi over 6 years ago in reply to Ryan Andrews

Intellectual 260 points

Thank you.

Data converters

Data converters forum

ADS1298RECGFE-PDK: ADS1298R