CSD95490Q5MC: CSD95490 TAO pin capacitor value

Hi Kokei,

In a multi-phase VR regulator, all TAO/Fault pins from CSD95490 power Stages can be connected together and monitored by Controller TSEN pin.

In this case , only the highest Power Stage device temperature will be measured and monitored. However,depending on the number of CSD95490 phases in your design, you must select a trade-off between TSEN noise filtering and Accuracy vs. reaction speed in case of a Fault condition.

For example, in a 6 phase VR application 470pF placed right at Power Stage pin and 1nF placed at controller gives a best trade off. That gives you a total 3.82nF capacitance, while CSD95490 has a 1mA source capability on TAO pin.

If your design uses a lower number of phases, then you can increase the 470p up to 1nF to get better noise filtering .

However, during a Fault condition CSD95490 will pull TAO line at 3.3V using 150ohm pull-up impedance. For proper Fault response, we don't recommend exceeding the designed  (150ohm * 3.8nF) time-constant.

Best regards.

Hi Kohei,

Thanks for your question!

The 470pF TAO cap on datasheet is for multi-phase design since one Power Stage needs to drive all the caps on TAO signal(including cap on controller TSEN pin and TAO caps for all Power Stages), the drive capability of TAO pin is much larger than 470pF. 

In addition, local TAO cap for each Power Stage is not  required (this is mentioned in datasheet), one cap at controller TSEN pin is good enough. 

Thanks!