As a simple project, I was trying to replicate an Arduino Nano, fabricating my own board. I'm using a
UA78M05 linear regulator to feed
5V from a
9V battery (see image below) as external power supply.
Now, this board uses an 6-pin IDC type connector for SPI programming. Since the 2nd and 6th pins of the IDC connector are, respectively,
GND, I'm applying a voltage to the output of the linear regulator. The problem is that the regulator immediately heat up (after maybe 10 seconds I can't touch it). Is it supposed to heat up like this and I simply forgot to put a heatsink? Or is there something wrong with the wiring? The rest of the board follows in the next image. All the parts were soldered by me and are SMDs on a board professionally frabicated (no home-made etching).
Edit 1: Following the suggestion of Dwayne, I hooked up a 1N4007 diode across the output and input pins. The result was that now the heat distributes across the two components: for the same amount of time during which I keep the battery connected (or the IDC connector), if there's the diode, the regulator will heat less but touching the diode you can feel it heated. Is this an expected behaviour or there's something wrong with wiring/power dissipation?