LTC2439-1

Hi!

We wanna use the LTC2439-1 configured with 16-Channel Single-Ended Inputs, the Reference-Voltage is 5.0V and the Input-Channel Voltages are from 0-5.0V

But the datasheet does not clearly describe the function for us with this configuration.

We are not sure if the LTC2439-1 converts a Input-Channel Voltage from 0-5V (CHx/COM) to a 16-Bit result (with the above decribed configuration) ?

Or the channel voltage must be between -FS (-0.5 * Vref) and +FS (0,5 * Vref) ?

Thank you !

Martin

  • 0
    •  Analog Employees 
    on Mar 15, 2019 9:45 PM over 1 year ago

    The absolute input voltage range for IN+ and IN- is GND-0.3V to VCC+0.3V so the input voltage range will be 0-2.5V with COM grounded. This is a bipolar part. With COM grounded you will have access to only half the input range.

  • Thank you for your reply ghoover !

    The absolute input voltage range is clear described in the datasheet, we understand this.

    We also suspect, that a input voltage of 0-5.0V (with Single-Ended-Inputs and Reference-Voltage of 5.0V) is converted into a 16-Bit value of 0-65535.
    But we are not sure, because we don`t find a clear statement for the conversion in Single-Ended mode in the datasheet.

    On some paragraphs in the datasheet the conversion is described for the bipolar differential input signal, but not for the single-ended.
    Only in the datasheet under "Input Data Format" (page 11, third paragraph) there is a indication to single-ended conversion.

    So can you confirm that a input voltage of 0-5.0V (with Single-Ended and Reference-Voltage of 5.0V), is converted into a 16-Bit value of 0-65535 ?

    Thank you !!

  • 0
    •  Analog Employees 
    on Mar 18, 2019 3:30 PM over 1 year ago in reply to Moscht

    My earlier reply was incorrect and I have edited it so that it does not confuse anyone else. This is a bipolar part. The input range is -0.5VREF to +0.5VREF. To use the full range of this part with COM held constant, it is necessary to bias COM at REF/2. The CH0 to CH15 inputs can then swing from 0-Vref.

    The output code is a 19-bit digital word. Bit 18 is an end of conversion signal. Bit 17 is a dummy that is always zero. Bit 16 is a sign bit that in conjunction with Bit 15 can be used as an over range and under range indication. Bit 15 through Bit 0 are the 16-bit data in two's complement format.