I’m having a temperature issue with the Venus GPS with SMA Connector board (PN# GPS-09133)
I’m intending to use this in an automotive application so I’m using the DC/DC converter board (PN#BOB-09370) , as it will provide clean power for the GPS from a 12v in car power system. I set up the trim on the power supply board with a 2.2K resistor for 3.3v and that looks clean and stable on the scope meter.
I set up the system on the bench powering the DC/DC board with my power supply set at 12.0V. With just the DC/DC board connected current draw from the power supply is 0.02A.
When I connect the GPS, the current draw jumps to .48-.52A and the Venus chip gets too hot for my liking. The LED comes on, as it should, but I’m concerned about the current draw/temperature.
Anyone have any tips/thoughts on what might be going on?
That current sounds WAY too high. Don’t keep running it under those conditions or something will be fried (or may already be fried).
I’m guessing that for some reason when loaded the BOB-09370 is outputting a higher voltage than it should, and this is causing the GPS module to heat up. If you dare, you could quickly run the setup again, and monitor the power supply with your scopemeter. If the voltage looks OK, it was probably an issue with the GPS modue from the start.
That BOB-09370 looks like massive overkill for your application (it can output 6A), but I don’t see why it would be doing this…
I chose that DC/DC converter as it had a lot of overhead to deal with the varied volatges that one might find in a car. While the current limit is very high for the application, it seemed like the right choice to me, but please let me know if I’m off track on this.
As a follow up, I tried to connect the Venus to my bench top power supply set at 3v. As soon as the Venus was connected it pulled the power supply down to 2.2V at .56A, and once again got “warm”.
I’m guessing that hot=dead.
While the led does still come on, I’m reluctant to connect the 232 interface to it for fear of taking another component out as well.
If you have any last ditch ideas on what I might try next, please let me know…but it looks to me it’s time to buck up and buy another module…
I don’t know what else you’re connecting the Venus module to, but obviously double check things to make sure nothing is shorted or connected incorrectly…
“it had a lot of overhead to deal with the varied volatges that one might find in a car”
“please let me know if I’m off track on this”
Sorry to tell you that, yes, you are off track on this. The 14 V input limit on the converter really isn’t high enough for an automotive application, nor does it have the overvoltage and reverse voltage protection you would want.
I am having a hard time imagining what you would need 6 A regulated output current for…
To get an idea of what you need for an automotive application, take a look at the LM2940 linear regulator. It’s not available in a 3.3 V output, but read through the datasheet regarding the operating voltage range and built-in protection circuitry to get some idea what you need to design for. There’s more to it, but this will give you a good place to start.
Oh, and BTW I would not be designing this for 12.0 V nominal. No correctly running car outputs 12.0 V. Most cars actually run at between 14.0 and 14.5 V nominal when the engine is running. Depending on how serious you are, you may also need to provide for dual-battery jumpstart conditions, where the tow truck guy is going to apply two fully-charged batteries in series (~13 V each, ~26 V total) to your poor circuit.