Problem with MC33269D-5.0

In MC33269D-5.0 voltage regulator, I see 3 pins, but second pin is not connected to board.

Datasheet says :

Heatsink surface (shown as terminal 4 in
case outline drawing) is connected to Pin 2.

...but heatsink surface also is not connected to board. 2 pin is not connected. Why ? On schematic I see it is... ??

but second pin is not connected to board.

The second pin is the voltage output. If it is not connected it is not working, therefore I think you are mistaken about this.

What board are you talking about, have you a close up picture? It could be on a track under the device if it is surface mounted.

Im talking about Arduino Duemilanove.
Schematic part IC4 (MC33269D-5.0).
Marked in red are pins of the voltage regulator. Pin 2 is connected to heat sink pad, but none of them is connected anywhere to the board, as I see.

Perhaps, anyone has schematic of board, which is checked in practice ?

If you are talking about the short pin in the middle, it is totally normal. The heatsink soldered to the board is the pin that needs to be soldered.

You can measure the voltages with a multimeter.

If you look at the pad you will see dimmed out Grey tracks going out from it. These are tracks on the other side of the board, the connection goes through the holes that surround the pad. These are known as plated through holes because the hole joins the top tracks to the bottom tracks. So pin 2 does go on to the 5V line of the rest of the circuit.
Can you see this?

But there is not conneection with "grey block" of 2 pin, with other ! I can't see it. If You can, plesae draw it. And if I look on oryginal piccture of board, I can't see connctions of pin 2 with surrounded vias .

If we look here :
we can not see the connection, but Eagle, say, that connection is. I dont understand it...

Here's a segment of the reference Diecimila board design "extra"-highlighted to show the connection to the heatsink area. Does that help?

( huh? Where did the picture go? Here's a link instead: )


means where ?

He meant this:

Which was showing embedded before but appears not to currently.


Big thanks for all :wink:

Only I wonder why in new Arduino 2009 there is not connections... I must check all "print board" with schematic.

@Phil, Im beginner in Eagle, but there also is not connection(in Your link As You see blue is a bottom layer, and there is not vias, or other connection with it.

@psu: that's not my link, it's the one that westfw posted, that was not showing before. :slight_smile: I know nothing of Eagle....


As You see blue is a bottom layer, and there is not vias, or other connection with it.

Huh? The light-blue link looks a bit white-ish under the read (grr. Don't like the Eagle 5 renderign), but it's definitely there and connected to the top red heatsink pad via the yellow vias. Other nodes in the connection are one side of the power select jumper, and one side of the post-regulator cap.

Are you expecting this to connect to the ground plane? On the 33269 (and most LDO regulators), the heatsink (and center tab) are connected to Vout, and Vout from the regulator on Arduino doesn't go very many places before it gets "switched" with the USB power.

(also, for some reason the Diecimila Eagle files, and perhaps the 2009 as well, are packaged with the "via" layer not displayed...)

I checked Your schema with Eagle project form Andruino web page - yes, are different.

Now, I check schematic with board scheme. Now I find 5 bad connected path (not connected). I think that Eagle have a bug in Board module.
e.g. element C12 one pin is not connected to nothing. If You want, can check it.

I downloaded the 2009 files and they look fine to me.
Don't forget to use the "ratsnest" command to fill in the GND (and other) polygons that cover both sides of the board. the C12 pin you complain about connects directly (and only) to the gnd polygons, as does the tab of the regulator (to smaller "+5V" polygons that are part heatsink.)

It works ! Big thanks !! :wink: