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ESD & low-voltage transient protection for 3.3V analog, digital, and power line

stanley
Prodigy 50 points
Other Parts Discussed in Thread: TPD4E1B06, STRIKE, ESD351

Hi E2E,

I would like to ask for help selecting a protection diode for my circuit, consisting of 3 simplified configurations:

1. High impedance precision analog line - no significant leakage allowed
2. Digital signal line to a microcontroller's GPIO - resistor to limit current and increase protection
3. Power line - 3.3V VDD for the microcontroller - bypass cap, but no resistor to avoid dissipation and save power (battery operated device)

 

In all three scenarios:

  • The operating voltage is 3.3V, with 3.9V being the absolute maximum rating
  • I want to protect against ESD events as well as potential transient voltages that could peak as low as 4V (which is still above the max rating)
  • For simplicity, let's assume all the signals are DC so I do not have a maximum capacitance requirement

Questions:

1. For the 1st scenario, I am thinking about using TPD4E1B06 due to its 0.5nA max leakage. Is it the best ultra-low-leakage choice, or would you recommend something else?

2. Regarding the 2nd and 3rd scenario, I have tried using the parametric search and found some candidates with VRWM of 3.6V, but I cannot find the clamp and breakdown voltage that would satisfy the requirement of protecting the circuit from surge as low as 4V, not allowing it to experience more than 3.9V, and having VHOLD above VRWM. Could you please recommend an ESD or TVS diode that could possibly work for both configurations?

Thank you.

Best regards,
Stanley

  • 0
    TI__Genius 14240 points

    Hi Stanley,

    The TPD4E1B06 has the lowest leake current in our portfolio so that is a good choice. 

    Clamping at 4 V when the working voltage is 3.6 V requires a deep snapback diode which we currently don't have. 

    ESD351 will have our best clamping performance at 3.6 V at 6 V for an 8kV ESD strike.

    Also the clamping voltage is a transient spec while the abs max from the MCU datasheet might not spec a transient abs max, only DC. There is typically some margin between the DC and transient abs max. 

    The leakage is also 0.1nA typical, the 10nA max is just a worst case. Here is a graph of the leakage current over the operating temperature.

    Regards,

    Sebastian 

  • 0
    Prodigy 50 points

    Hi Sebastian,

    Thank you for your answer.
    The charts make sense, but as you said, the datasheet does not specify the TLP rating.

    I would like to ask one more question regarding the TPD4E1B06. If I want to use just 1 input out of 4, can I connect all of them together such that the diodes are in parallel? I understand it will increase the leakage, and during an ESD event it might still be just one of the diodes taking most of the load, but I would still expect this to decrease the chance of failure. Is it correct?

    Thank you.

  • 0 in reply to stanley
    TI__Genius 14240 points

    Hi Stanley,

    You can tie the inputs together but it wouldn't decrease your chance of failure from ESD. Each channel only offers 12kV IEC ESD protection, this will not improve by tying the inputs together. Also as you mentioned one of the diodes could shunt most of the current since each channel won't have an identical dynamic resistance. 

    Regards,

    Sebastian 

  • 0 in reply to Sebastian Muriel
    Prodigy 50 points

    Hi Sebastian,

    Ok, I see. Theoretically, if leakage current was not an issue, would you then recommend a different diode configuration for better ESD protection (for example diode array + TVS)?

    Thank you.

  • +1 in reply to stanley
    TI__Genius 14240 points

    Hi Stanley,

    If you're looking for better overall system level ESD protection, the TPD4E1B06 only has a 12kV IEC ESD rating where as some of our devices offer up to 30kV. Also most of our newer devices will offer better clamping voltage, which will ultimately determine if an ESD diode can protect the downstream MCU.

    I would recommend the ESD351. It offers pretty low leakage and will have the highest IEC ESD surge rating of 30kV. It also has the best clamping performance of our 3.6 V devices.

    Regards,

    Sebastian 

  • 0 in reply to Sebastian Muriel
    Prodigy 50 points

    Hi Sebastian,

    Perfect. Thank you very much for help and have a nice day.

    Regards,
    Stanley