SLVSEQ2B September 2018 – November 2021 TVS1401
PRODUCTION DATA
If the TVS1401 is in place to protect the device, the voltage will rise to the breakdown of the diode at 17.6 V during a surge event. The TVS0701 will then turn on to shunt the surge current to ground. With the low dynamic resistance of the TVS1401, large amounts of surge current will have minimal impact on the clamping voltage. The dynamic resistance of the TVS1401 is around 70 mΩ, which means a 25-A surge current will cause a voltage raise of 25 A × 70 mΩ = 1.75 V. Because the device turns on at 17.6 V, this means the ADC input will be exposed to a maximum of 17.6 V + 1.75 V = 19.35 V during surge pulses, well within the ADS8689 absolute maximum to ensure robust protection of the circuit. The same magnitude of voltage will be seen during a negative pulse, still safely protecting the system.
In addition, the low leakage and capacitance of the TVS1401 assures low input distortion. At 14 V, giving margin on the ±12.288 V range of the ADS8689, the device will see typical 1.1-nA leakage, which will have minimal effect on the overall system. The TVS1401 low capacitance of 68 pF will also cause less effect on signal integrity compared to industry standard devices like the SMBJ14CA which has 1500 pF of capacitance and can cause up to 3 dB of THD attenuation in measured systems.
Finally, the small size of the device also improves fault protection by lowering the effect of fault current coupling onto neighboring traces. The small form factor of the TVS1401 allows the device to be placed extremely close to the input connector, which lowers the length of the path fault current going through the system compared to larger protection solutions.