I made a 2560 core board, and I drive it with a 5 V power supply. I loaded a blink ino. But the chip feels hotter than a regular arduino 2560 board. And when I measure the current, it is around 200mA. I don't think there are anything much more than the bare chip.
The resonator is a regular 16MHz one, shown in some BOM of a regular 2560 R3. Is this something expected? Is there any thing I can do to improve this power efficiency like fuse setting?
Can you include a larger schematic? I can barely read that one. And the grid makes it even harder.
Are you connecting 5V to X1? The diode and regulator (? can't read it) will knock the 5V down a lot.
A 2560 needs 4.5V minimum.
A 2560V can run on lower voltage.
I have uploaded the schematic and in a larger resolution. After downloading it one can see the details better. I don't have the regulator in this circuit, because I powered it using a 5V supply. It is quite strange that this consumes that much power. I think the next what I can try is to swap the chip of a regular arduino 2560 board with the chip I used on this.
Thanks for the decoupling caps suffestion. I didn't explicitly set any fuses yet. Because I tested it by first loading the bootloader of a regular 2560 r3 using the ide and icsp pins and then uploading sketches using the serial port of this board with the arduino ide and manually pressed the reset button. I assume the fuses settings should be same as a regular 2560 r3 .
What type of buzzer are you using? Could you check its resistance? I assume you set PB0 at LOW and it wouldn't matter the resistance but just in case you set it HIGH, there could be some current through the buzzer.