JAJSEX4A December 2017 – March 2018 TVS1400
PRODUCTION DATA.
If the TVS1400 is in place to protect the device, during a surge event the voltage will rise to the breakdown of the diode at 16.8 V, and then the TVS1400 will turn on, shunting the surge current to ground. With the low dynamic resistance of the TVS1400, even large amounts of surge current will have minimal impact on the clamping voltage. The dynamic resistance of the TVS1400 is around 30 mΩ, which means 43 A of surge current will cause a voltage raise of 43 A × 30 mΩ = 1.29 V. Because the device turns on at 16.8 V, this means the ADC input will be exposed to a maximum of 16.8 V + 1.29 V = 18.09 V during surge pulses, well within the ADS8689 absolute maximum. This pulse is shown in and ensures robust protection of your circuit.
In addition, the low leakage and capacitance of the TVS1400 guarantees low input distortion. At 14 V, giving margin on the ±12.288 V range of the ADS8689, the device will see typical 10 nA leakage, which will have minimal effect on the overall system. The TVS1400 low capacitance of 125 pF will also cause less effect on signal integrity compared to industry standard devices like the SMBJ14A 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 TVS1400 allows the device to be placed extremely close to the input connector, lowering the length of the path fault current will take through the system compared to larger protection solutions.