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ADS1258: Power-Up

Eren Erdogan
Intellectual 280 points
Part Number: ADS1258

Hi all,

I have a question about power-up of ADS1258.

In page 24, the datasheet of ADS1258 states that “The analog and digital supplies should be applied before any analog or digital input is driven”

I’m wondering that what happens if I don’t apply analog supply while any analog input is driven?

If I have to do this, what precautions can be taken?

Regards,

Eren

  • 0
    TI__Mastermind 44680 points
    Hi Eren,

    The ADS1258 inputs pins have ESD diode connections to their corresponding (analog or digital) supplies rails. Connecting an input pin to a signal before power has been supplied may result in the ESD diode becoming forward biased and "back powering" the supply rails from the input voltage.

    From a system perspective, you'll have to evaluate if there are any other devices on the supply rail that might not tolerate this effect and you might consider adding a TVS diode between the supply rail and ground, to ensure that the supply voltage gets clamped above 5V, in case of an input overvoltage.

    From the ADS1258's perspective, you'll want to make sure that any input signals that cause the ESD diodes to conduct are current limited to 10 mA or less. Continuous currents above 10 mA violate the device's absolute maximum ratings and may damage the IC. To help protect the ADS1258, you can place series resistors on each of the analog inputs (as would typically be used for RC filtering) and size these resistors such that your input signal would not conduct more than 10 mA of current through these resistors. So for example, if it is possible for up to 10V to be applied to an input pin, then you want at least a 1kOhm series resistor to limit the current to 10 mA.