Part Number: ADS1299
Dear TI Experts,
We have designed a medical device using ADS1299IPAG, and this device is in the process of IEC 60601 certification.
During certification, our testing agent has informed us that our design does not meet IEC60601-1 section 8.9 (creepage and clearance) requirement because of the spacing within the package (not the external pin spacing outside of package) of ADS1299. Because the spacing does not meet creepage and clearance requirement (1.7mm creepage and 0.8mm clearance), they assume there is an automatic short between the ADS1299 supply voltage rails (AVDD, AVSS, DVDD etc.) to the front-end channels (IN1P, IN1N…. IN8P, IN8N), and this short is considered a normal condition, not a failure condition.
At our front-end, we have 51Kohm resistors and clamps between the patient and the ADS1299. Therefore, if there is a short between the supply voltage (+/-2.5V) and the front-end channel, the patient is exposed to <50uA of auxiliary current. For single fault condition, our device would pass the patient auxiliary current requirement, because the required current limit is 50uA. However, to pass the normal condition requirement, our device needs to reduce the auxiliary current down to 10uA or less. Our current device is not able to pass this criteria.
To pass the criteria mentioned above, we need to ensure one of the following is met:
1. Increase the front-end resistor to 250Kohm (2.5V/10uA). This change will increase our common mode noise and Gaussian noise drastically. The datasheet for ADS1299 does not provide tolerance for the 20pF input capacitance. Can you let us know the tolerance of the input capacitance?
2. The ADS1299 has sufficient internal creepage and clearance, or the creepage and clearance criteria should not apply for the internal of ADS1299. We need to justify this fact somehow.
Would you be able to provide us assistance in this matter? Perhaps you have faced similar situation in the past with your other customers.
Thank you.
