What will happen to F-RAM if it is turned ON and OFF continuously? Is it required to meet the tPU and tPD timings?
It is not necessary to meet the timings tPU (Power-up to first access) and tPD (last access to power down) during power up and power down. F-RAM can be turned ON and OFF continuously. As long as the VDD slopes, measured at any point, meets the power-up ramp rate (tVR) and power-down ramp rate (tVF), and the voltage is monotonic during power up and power down, there are no issues. F-RAM will continue to function normally in the next power up.