SETUP: I've put together a board comprised of:
- 24 V DC Supply voltage connected to 60 Ohm (10 W) Resistor that is in series with a LM7805C (5V Regulator). The LM7805C has a .33 uF cap on the Vin terminal, GND is connected to GND, and a 0.1 uF cap on the Vout terminal. When I measured my current coming out of this, I saw 400 mA (like I expected).
- Out of the LM7805C, I have an ATMega328PA that has a crystal oscillator connected to it and is connected to a Adafruit NFC board via SPI in the same way as this setup.
- The NI hex buffer (HEF4050B) you see is also attached to Vout of the LM7805 but using a resistive voltage divider, I "feed it" 3.3 V
- The Adafruit PN532 (NFC) board is connected also at Vout of the LM7805 and being supplied 5 V.
ISSUE: I'm currently facing a low current problem --- there's not enough current flowing to the PN532 board --- it requires about 150 mA to function appropriately, but when I put in my ATMega, my current drops to about 20 mA. Should I need to have a separate regulator for the PN532 and the 4050?
(click to view full size)