The value of the input capacitor is approximately 4 pF. It can be calculated as follows:

Conditions: Fast power mode, MCLK = 32.768MHz, MCLK_div = 4, analog input precharge buffer off

Formula: I = CVF

The analog input current has two components, differential and common mode, so total current for this example is equal to 65uA/V (from the Datasheet)

It is important to remember that the modulator switches at twice the Fmod frequency. The Fmod frequency is MCLK/MCLK_div = 8.192MHz. Switching at twice this is = 16.384MHz

I = CVF and so:

C = I / (F*V) as the current is in amps per volts the voltages cancel to give:

Hi,

The value of the input capacitor is approximately 4 pF. It can be calculated as follows:

Conditions: Fast power mode, MCLK = 32.768MHz, MCLK_div = 4, analog input precharge buffer offFormula:I = CVFThe analog input current has two components, differential and common mode, so total current for this example is equal to 65uA/V (from the Datasheet)

It is important to remember that the modulator switches at twice the Fmod frequency. The Fmod frequency is MCLK/MCLK_div = 8.192MHz. Switching at twice this is = 16.384MHz

I = CVF and so:

C = I / (F*V) as the current is in amps per volts the voltages cancel to give:

C = 65uA / 16.384MHz = 3.967pF

The following application note can be used as a starting point to select a suitable driver amplifier: Modular Data Acquisition (DAQ) Footprint Using the AD7768/AD7768-4

Regards

Niall