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Dear Technical Support Team,
The ADS7805U describes an offset adjustment circuit.
However, ADS8515IDB datasheet does not describe the offset adjustment circuit.
Q1
We are considering replacing from ADS7805U to ADS8515IDB.
If I'd like to install a similar offset circuit in ADS8515IDB,
How is the resistor value should be set for the offset circuit?
Q2
Is there any reason why the offset circuit is no longer listed for the ADS8515IDB?
Best Regards,
ttd
Hi ttd,
Figure 25 in the ADS8515 datasheet performs the same gain adjust function as figure 6 in the ADS7805 datasheet. The main difference is that the external resistors (200 ohm and 33.2k ohm) are no longer needed with the ADS8515, which is where the offset trim came from. If you want to maintain the same ADS7805 circuit, please look at the ADS8505 as an alternate device.
Hi Tom,
Thank you for your reply.
The ADS8505 cannot be used because digital I/F is 3.3V.
Q3:
Please introduce any candidate products with the following specifications.
Resolution : 16bit
Sampling : 100kHz or more
Input voltage range: ±10V
Number of input channels : 1
Digital power supply voltage: 3.3V
Analog power supply voltage: 5V
Operating temperature: -20 to 70°C
I/F : Parallel (16bit)
Package: Any SMD package is acceptable
Q4:
Also, I would like to know the following additional information.
You said:
The external resistors (200 ohm and 33.2k ohm) are no longer needed with the ADS8515.
→ Is it correct to understand that the offset is no longer displaced?
Does this mean that the offset has become smaller and no adjustment is needed?(the offset error of ADS8515 is about the same as the error due to ADS7805 with offset adjustment circuit)
Best Regards,
ttd
Hi ttd,
The ADS8517 has better offset, so that might be an option for you.
The first page of the ADS7085 and ADS8515 datasheets show the internal resistors found within the part. They are a bit different and they use a different internal reference as well. You could implement the offset adjustment, but the resistor values would need to change.
Hi Tom,
Thank you for your reply.
I have question about ADS8518.
You said:
You could implement the offset adjustment, but the resistor values would need to change.
⇒Could you please suggest the resistor values?
in other ways, do you have application note with offset adjustment with AMP, could you share it?
Best Regards,
ttd
Hey ttd,
I took a closer look at the ADS8515 and with the difference in reference voltage and internal resistors, its offset is better than the ADS7805. The main source of error there is with the internal reference. The ADS8517 has better offset as I mentioned before, so take a look at that as well.