Part Number: ADS1299
Hi TI team,
we are designing ADS1299 for EEG application. ADS1299 self signal test is OK.
I input an external sine wave to the ADS1299, but I can't check the output.
Input sine wave : 2Hz, 10mVpp (Input on pin 16.)
Please review the single-ended hardware configuration for any problems.
I review your schematic and I have one recommendation to how the VREFP and VREFN signals are driven. For your bipolar supplies with external reference operation, we recommend to drive the VREFN signal with AVSS (-2.5V in your case) and VREFP to AVSS + VREF (VREF = 4.096V in your design). Please refer to Section 7.3 for recommended operating conditions for Voltage Reference inputs.
For your design, you should be able to apply the single ended sine wave to CH1 (2Hz, 10mVpp) with common-mode voltage (Vcm) at mid supply.
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In reply to TCT:
Thank you for your quickly support.
Need to change the VREFN voltage to -2.5V?Doesn't need to change the VREFP voltage?
Should VREFP-VREFN be greater than or equal to 4.5V?
In reply to Downey Kim:
For your bipolar supply operation, as stated the VREFN voltage will be -2.5V (AVSS) in your application. VREFP will also need to be changed and driven to AVSS + VREF (-2.5V + 4.096V) from your design. For the best performance of the device, the typical value for VREF = VREFP - VREFN should be 4.5V as stated in the datasheet.
You can also refer to the ADS1299EEG-FE EVM schematic in the user's guide (Page 58 and 61) for how to drive the VREFP and VREFN pins with external reference driver circuit.
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