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ADS1261: Input protection recommendation

Kai Hsiao
Guru 12675 points

Part Number: ADS1261

Hi Sir 

our customer request analog input need to have below with ADS1261 

1. common voltage protect is 25Vdc

2. over voltage protect is +/- 120Vdc

Have any solution can do ? differential amp or something else 

  • 0
    TI__Mastermind 44820 points

    Hi Kai,

    What is the maximum current that the input source would be able to provide if shorted?

    We have some bi-directional TVS diodes that might be helpful for clamping the input voltage.

    Chances are the customer would need to use a combination of input protection techniques, such as voltage clamping and current limiting. A generic protection scheme might look something like this...

    Notes:

    • It is very important to pay attention to the diode leakages, as these leakage currents will degrade system accuracy.
    • Take care to avoid the possibility of LC resonance, especially if pure inductance are used in place of Ferrite beads, by ensuring that the LC resonator is properly dampened.
    • The amount of series resistance to use should also be considered carefully. Higher resistance values will provide better current limiting, but will also result in higher noise, offset, and offset drift due to diode leakage currents or input bias currents.

  • 0 in reply to Christopher Hall
    Guru 12675 points

    Hi Chris

    1. you mean below red point short to GND ,what's the maximum current that current source can supply ,is it correct ? 

    2. do you have TI design include the protection circuit that i can refer first ?

  • 0 in reply to Kai Hsiao
    TI__Mastermind 44820 points
    Hi Kai,

    The red point is the input voltage to the customer's system. The first resistor and TVS diode are optional, but in general I would recommend trying to shunt any overvoltage or EMI signal to earth/chasis ground before entering the system as this helps to protect sensitive components inside the system.

    Most of our ADCs can tolerate up to 10mA of continuous current flow through the internal ESD diodes; therefore, the input protection circuitry should ensure that current flow is limited to something below this value to prevent damage to the IC.

    The most relevant TI design I can point to is www.ti.com/.../TIDA-00548. I hope that helps!