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ADS1299: Power Sequencing Digital and Analog Inputs

Simon Wong1
Prodigy 10 points
Part Number: ADS1299

In section 11.1 of the data sheet, it mentions that "before device power up, all digital inputs must be low. . . until power supplies have stabilized."

What are the consequences if digital inputs are high at startup?

In my current design I have the following pins normally pulled up to high simultaneously with the supply power.

CS*

RESET*

PWDN*

CLKSEL

Thank you

  • 0
    TI__Guru 55232 points

    Hi Simon,

    More than likely the device will be put into an unknown state if the power-up sequencing is not followed properly. This results in incorrect device ID and false readings from the device. 

  • 0
    TI__Guru 66346 points

    HI Simon,

    The primary concern is that the pins could become damaged if voltage is applied to the pins before DVDD is enabled. For example, if your MCU is powered before DVDD of the ADS1299 is enabled, the MCU SPI/GPIO outputs may apply voltage to the ADS1299 digital inputs, which can damage the device.

    If the digital inputs are simply connected to pull-up resistors, the voltage on these pins can be allowed to rise simultaneously with the digital power supply.

    Any MCU output pins which are connected to the ADS1299 digital inputs should remain tri-stated (high-impedance) until DVDD is established. After all supplies are established, reset the ADS1299 to ensure the device is powered-up in a known state. You can verify this by reading the Device ID, per Alex's response.

    Best regards,