Part Number: AFE159RP3
Other Parts Discussed in Thread: AFE159RP4, ADS1298
Hi! The AFE159RP4 eval kit protects ECG leads and respiration input and output leads with a TVS to ground on the patient side of a final 1 kOhms series resistor between the TVS and the AFE, in addition to different components between TVS and patient, such as resistors or capacitors, depending on the function of the AFE pin. However, the eval kit is described as NOT being defibrillation protected.
The Analog Devices ADAS1000 documentation provides the following two suggestions for ECG lead defibrillation protection:
- Either resistor 4 kOhms between patient and circuit, then Argon/Neon bulb as "spark gap" to ground, 500 Ohms series resistor, one Littelfuse SP724 TVS channel to ground, then final 500 Ohms series resistor to AFE
- Or, alternatively, 4,5 kOhms series resistor between patient and circuit, then one or two parallel SP724 TVS channels to ground, then final 500 Ohms series resistor to AFE
If surge sensitivity of chips in the AFE159 family is similar, then the circuit used in the AFE159RP4 eval kit MIGHT already be sufficient to protect the AFE159 pins from defibrillation pulses?
The input protection in the ADS1298 eval kit documentation (no respiration, NOT defibrillation protected) was quite different: Series resistor 22.1 kOhms between patient and circuit, then 47 pF to ground, another 10 kOhms series resistor, another 47 pF to ground, clamping diodes to AVDD and AVSS.
While the circuit would not be suitable for respiration pins, due to the large series resistances, using that circuit with surge-proof resistors and capacitors MIGHT be sufficient to provide defibrillation protection for ADS129x family AFE?
Can you make recommendations for defibrillation protection of AFE159 chips, both for ECG and for respiration pins? Thank you!