I am building a circuit that will run off the 12V battery in a bus. I need two supplies - 5V and 3.3V, the overall current consumption being <200mA. I have an LM7805 to generate the 5V supply and it then drives an LD1117-.3.3, to generate the 3.3V supply. The circuit I have designed is shown in the figure below.. My questions are as follows:
Is it OK to also add a 470uF electrolytic cap on the input of LM7805? I am hoping for additional protection against fluctuations in the 12V supply from the bus battery.
Is it OK to skip the 0.1uF on the input of the LD1117-3.3 since the output of the LM7805 already has a cap of this value?
The LM7805 recommends a smaller cap on the output compared to that on the input, whereas the LD1117-3.3 recommends a larger cap on the output compared to that on the input - any insights in to why this is the case? I am just trying to understand whether there are any gotchas in connecting the output of the LM7805 to the input of the LD1117-3.3!
Can the 0.33uf and 0.1uF be ceramic (SMT) caps?
I have some off the shelf power regulator boards that use the LM7805 but have a very large electrolytic cap (1000uF) on the input and another electrolytic cap (10uF) on the output. Why would they deviate from the recommended values of the decoupling caps?
Thank you very much for your help.