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ADS124S08: Capacitance of Pins

Part Number: ADS124S08

Hi Bob, 

This E2E Post says to check the ADS124S08 IBIS model to get the pin capacitances.
I opened the IBIS model in a text editor, but the value under C_pin was "NA" for all pins...for both package types.

Could you provide the pin capacitances for the following...?

a) Analog Input Pins
b) Digital Input Pins
c) Digital Output Pins

Regards,
Darren

  • Hi Darren,

    What we have is in the IBIS model.  There are the package (pkg) values which would be the same for each pin.  That is why it is shown as NA.  The 'pkg' values only include the package to die connection.  The die capacitance (C_comp) is the value based on analysis, voltage range, etc..  The IBIS model itself is used for signal integrity of the digital and supply pins.  Which specific models are available are given under 'model_name', and they include:

    • INPUT
    • OUTPUT
    • CSN
    • POWER
    • GND

    At the package section of the IBIS model you will see which pins have provided models.  The input values would be computed based on the following schematic:

    The digital output would include loading Cref and Rref following the output stage.  In the end, the IBIS models are designed for digital analysis of logic high and logic low at various voltage supply levels.  There is no good use case for an analog model as the analog is much more dynamic and in the end will be dominated by any external cap loading by the analog input filters, bypass caps, etc..  As the analog inputs are CMOS, the best I can give you is the C_pkg values as shown in the IBIS model.  And if you wanted to include the input capacitance values for C_comp that would be appropriate.

    Best regards,

    Bob B