SuperCap in Xilinx Zynq

Hello guys,

I need to gurantee the supply of the Xilinx Zynq for 0.5 sec before the chip is shutted down because whichever current supply problem.The reason is because I need to save some important data in memory. The question is if there is some way to keep the chip alive during a minimum time. I have been having a look and the Xilinx Zynq 7020 has a VBAT pin, but I think that it is not valid for my purpose...

Any idea??

Greetings,

EP

Hi,

what is your power source? --> try to generate an early_power_fail_signal.

Maybe: AC --> rectifier --> bulk capacitor --> stepDown --> FPGA
Try to detect AC_loss.
* generate in interrupt
* switch OFF all unnecessary load
Then the bulk capacitor needs to provide the mount of energy
The step down will keep the FPGA supply stable.

****
some calculation:
Lets say you have a 0.1F supercap connected to 3V3.
On power loss maybe you can work down to 2.8V before a reset is asserted.
The available energy is (0.5 * 3.3V * 3.3V * 0.1F) - (0.5 * 2.8V * 2.8V * 0.1F) = 0.1525Ws
This is only 28% of the initially available capacitor energy.
And the voltage is continously falling.

Let´s say you have a 12V supply and a stepdown that works down to 4V input voltage.
Then you can use 89% of the available capacitor energy ... and the FPGA voltage is constant.
0.152Ws / (80% SMPS_efficiency * 89% capacitor_usage) = 0.215Ws capacitor energy @12V
--> use a 3300uF capacitor at 12V

Klaus