Hi,
1. Which capacitor does Cpd refer to? I noticed that Cpd is generally marked separately from Ci/Co. In which case do we need to consider the Cpd parameter?
2. What is the difference between ΔICC and ICC? Looking at the test conditions alone, it seems that there is not much difference. Under what circumstances do we need to consider ΔICC?
Regards,
Charlie
Hi Charlie,
Cpd is a measurement of the internal parasitic capacitances in a device and can be used as an approximation for dynamic power losses. You can learn more about this in this app note: CMOS Power Consumption and CPD Calculation. Cpd should be considered when the switching speed is very fast, so dynamic losses are higher.
The Icc is a measurement of the supply current when the device is in stable operation, so the input is either GND or VCC. This is the ideal operating case. The ΔIcc is measured with the input at a different operating point, Vcc - 0.6 for your device. In this operation, there is more leakage through the "off" FET, leading to more current use. ΔIcc can be considered when the input voltage is less than Vcc for a high signal and more than ground for a low signal.
Importantly, both values are for specific test cases and should not be considered absolute ratings.
You may also find this FAQ helpful: [FAQ] How does a slow or floating input affect a CMOS device?
Best,
Ian
