PSOC6 Vbackup Questions

[MiRo_263836]

On page 214 (section 19.2) https://www.cypress.com/file/385621/download it describes a default setting of the backup power domain to be Vddd if brown-out detect is enabled and no brown out event occurred.  Looking at simplified schematics I see it explicitly connected  to the Vdd pin or a separate power supply between 1.4 and 3.6 V.  Could anything go wrong if the vbackup pin is only connected to a small capacitor and nothing else?

[DheerajK_81 · Accepted solution]

Hello @MiRo_263836 ,

if you set VBACKUP_CTL to 0, it automatically selects VDDD if its brownout detector says it is valid. If the brownout says its not valid, then use VMAX which is the highest of VDDD or VBACKUP. Hope this clarifies your query.

Regarding connecting a capacitor to the Vbackup, it's not a problem. You could use the PSoC6 BLE Pioneer Kit schematic for reference. It uses a 330 mF super-capacitor for backup domain supply (Vbackup) as shown below:

The SW7 switch, switches the Vbackup supply connection to PSoC 6 MCU between VDDD and the super-capacitor. Please note that the I/Os referring to this domain will leak current if the VBACKUP feature is not enabled. When the capacitor is discharged, a brown out event will occur and the device is reset. 

Hope this helps 🙂

Regards,
Dheeraj

[MiRo_263836]

Thank you, Dheeraj.  That answers the question.