ADS125H02: For Vrms at 40ksps

Ryu Yamashita

Part Number: ADS125H02

Tool/software:

Hi team,

I plotted the Vrms characteristics on an actual device with Gain=128 to see if it would be as shown in Table 2 on p22 of the datasheet.
The results were as shown in the data sheet except at 40 ksps, but at 40 ksps there was a large discrepancy. （The result was as shown in the datasheet except at 40 ksps (about 2.5).
I am wondering if this is due to the fact that the internal clock changes at 40 ksps, which may cause the discrepancy.
Also, if the deviation is not correct, is there anything I should pay attention to as a setting value?

Regards,
Ryu.

9 months ago

0 Bryan Lizon86 9 months ago

TI__Mastermind 47091 points

Hi Ryu Yamashita,

Can you post your data (both good and bad) so we can understand what you are measuring at low data rates and high data rates?

-Bryan

0 Ryu Yamashita 9 months ago in reply to Bryan Lizon86

Genius 3170 points

Hi Bryan,

The Vrms value is checked.
At 40ksps, the datasheet value is about 1.8, but the actual measured value was about 2.5.
At other sampling rates, the values were the same as on the data sheet.

Regards,
Ryu.

0 Bryan Lizon86 9 months ago in reply to Ryu Yamashita

TI__Mastermind 47091 points

Hi Ryu Yamashita,

How did you measure the data? Can you describe the exact setup?

Are you using our EVM, or your own custom board?

-Bryan

0 Ryu Yamashita 9 months ago in reply to Bryan Lizon86

Genius 3170 points

Hi Bryan,

Measured using EVM.

Regards,
Ryu.

0 Bryan Lizon86 9 months ago in reply to Ryu Yamashita

TI__Mastermind 47091 points

Hi Ryu Yamashita,

In my previous post, I asked:

Bryan Lizon86 said:
How did you measure the data? Can you describe the exact setup?

Can you please provide answers to my questions? The more detailed the better. Include diagrams if you can.

On the other hand, the less info you provide to us, the longer it will take to resolve your issue. So please help us, help you

-Bryan

0 Ryu Yamashita 9 months ago in reply to Bryan Lizon86

Genius 3170 points

Hi Bryan,

The register settings are as follows

[ADS125H02 Register Settings]
ID 61
STATUS0 01
MODE0 80
MODE1 00
MODE2 00
MODE3 00
REF 0A
OFCAL0 00
OFCAL1 00
OFCAL2 00
FSCAL0 00
FSCAL1 00
FSCAL2 40
IMUX FF
IMAG 00
RESERVED 00
MODE4 5B
STATUS1 00
STATUS2 01

Regards,
Ryu.

+1 Bryan Lizon86 9 months ago in reply to Ryu Yamashita

TI__Mastermind 47091 points

Hi Ryu Yamashita,

You are showing MODE1 = 00, which sets DELAY = 0000. This is not recommended when data rate = 25.6kSPS or 40kSPS, and is shown in the datasheet (and below)

I tried DELAY = 0000 and DELAY = 0001 on my EVM, and reported the results below. You can see that the "noise" is almost doubled for DELAY = 0000 compared to DELAY = 0001. However, this not really noise, but settling error

With DELAY = 0001 (noise = 372.5 codes)

With DELAY = 0000 (noise = 637.8 codes)

-Bryan

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ADS125H02: For Vrms at 40ksps