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ADS1271: MODE pin operation in HighResolution mode

yuta_hiroi
Prodigy 30 points
Part Number: ADS1271

Tool/software:

Hi, 

I am currently using the ADS1271IBPW in High Resolution mode.
The MODE pin is floating, but when I observe the MODE pin waveform while the ADC is running, I can see a constant 1/4096 CLK.

Is this normal behavior in High Resolution mode?

Below is a brief summary of the ADC interface information:


・Not daisy-chained
・FORMAT pin = Low (SPI)
・CLK = 26.214MHz (51.2kSPS) *MCU output
・SCLK = 6.554MHz *MCU output
・DIN/DOUT/DRDY/SYNC = MCU connected
・DVDD = 3.3V

  • 0
    TI__Mastermind 46560 points

    Hello Yuta Hiroi,

    Yes, the ADS1271 uses an internal clock source to drive the MODE pin through a high impedance resistor (internal clock and resistor).  When the pin is floating, the pin is clocked and the ADC detects this to determine the pin is floating.  Connecting the pin to DGND or DVDD over-rides the internal clock circuit for a high or low state.

    In order for this pin to work correctly when floating, the total capacitance to DGND should be less than 100pF and any resistive loads should be greater than 10MOHM to ensure proper operation.

    Regards,
    Keith Nicholas
    Precision ADC Applications

  • 0 in reply to Keith Nicholas
    Prodigy 30 points

    Thank you. I'll take that into consideration.