Stellarcore
New Member
Hello folks,
I'm running a PIC16LF4585 at low voltage (3.3V) so that I can interface directly to an SD card without any level conversion circuitry.
I'm using an LM2936 LDO regulator to supply the PIC. I have a 0.1uF cap on the input and output of the regulator as well as a larger 47uF electrolytic cap on the output of the regulator to keep things stable.
The problem I'm having is that when I kill the power and bring it back up before the 47uF cap has discharged through leakage currents or whatever, the PIC wont start. I either have to remove the PIC from the socket and drop it back in, or short the cap to discharge it completely before the PIC will start back up.
In order to get the PIC to operate at low voltage, it was neccessary to disable brown out detection. My theory is that the PIC is not shutting down correctly when the power goes down leaving the PIC stuck in some kind of quasi non functioning state.
Can anybody think of a simple solution to this problem? One solution that I thought of could be to put a resistor between the cap and ground so that on power down, the cap will discharge quicker, but I'd prefer a better solution.
Perhaps a circuit that toggles the RESET pin on the PIC when the voltage drops below an operating level?
Thanks for your help.
I'm running a PIC16LF4585 at low voltage (3.3V) so that I can interface directly to an SD card without any level conversion circuitry.
I'm using an LM2936 LDO regulator to supply the PIC. I have a 0.1uF cap on the input and output of the regulator as well as a larger 47uF electrolytic cap on the output of the regulator to keep things stable.
The problem I'm having is that when I kill the power and bring it back up before the 47uF cap has discharged through leakage currents or whatever, the PIC wont start. I either have to remove the PIC from the socket and drop it back in, or short the cap to discharge it completely before the PIC will start back up.
In order to get the PIC to operate at low voltage, it was neccessary to disable brown out detection. My theory is that the PIC is not shutting down correctly when the power goes down leaving the PIC stuck in some kind of quasi non functioning state.
Can anybody think of a simple solution to this problem? One solution that I thought of could be to put a resistor between the cap and ground so that on power down, the cap will discharge quicker, but I'd prefer a better solution.
Perhaps a circuit that toggles the RESET pin on the PIC when the voltage drops below an operating level?
Thanks for your help.