Hi,
I need to replace the voltage regulator on my arduino NG. The schematic calls it a "7805DT". This isn't a real part number. The 7805 chips I've found don't seem to be fully compatible. Does anyone know what it is?
Why don't the schematics/layouts include part lists?
Thanks,
It's a 7805.
ICs frequently come in different packages. The 7805 is one of those that has been around long enough and is so popular that it comes in several varieties. Between 30 seconds with google and the parts I've seen in person, there are at least:
D-PAK package - the packge on the Arduino NG
TO-220 - the large package you're probably used to seeing
TO-92 - typical package for discrete transistors, also used by the 78L05 and the DS1820 1-wire temp sensor
SOIC-8 - surface mount package
... and National has a tiny thing they call a bump SMD or something like that.
I want to say I've seen it in SOT-23, but I could have dreamed that one up.
Vendor part numbers vary a bit, too. I think a likely designation for the Arduino NG's regulator is 78M05. Letters after the number are sometimes vendor specific, and tell you things like tolerances, temperature ranges, or what sort of packaging they're shipped in.
-j
I did check.
The 7805 on the NG board is a D-PAK with 3 pins: VI, gnd and VO. The 78M05 in D-PAK on octopart has the middle pin clipped and is grounded through the heat sink. I can't find a D-PAK that actually has a gnd pin. That's why I'm asking for the exact part number.
Thanks,
It's just a plain old boring 7805 - nothing to stress about. The most common (and probably the cheapest) package is TO-220 which will fit just fine on the NG board.
You can get them from Digikey for $0.47/each, or if you want to spend more you can get them from Radio Shack for $1.59/each.
etracer: The TO-220 won't work on the NG - no through-holes, and the pads are too close together.
My NG has the D-PAK with the clipped middle pin. 78M05C is the part number on mine.
It is common on packages like the D-PAK and TO-220 to use the heat sink tab as ground, also. That's what the D-PAK on my NG does - two pins plus the tab are soldered, no middle "ground" pin. It looks exactly like the DPAK-3 in this datasheet.
-j
Ah, so the heat sink is grounded too? See, that's not on the schematic. Ok.
Thank you,
Ah, so the heat sink is grounded too? See, that's not on the schematic. Ok.
Thank you,
hey
that's true. The reason that schematics can't be relied on to show you the physical connections for specific packages is that there are so many packages available. On the Diecimila, for example, the regulator is the same package as the regulator on the NG, but the Diecimila regulator's case is connected to +5. It always pays to check the datasheet.
D