I have digged a lot of google pages to find any information why UBlox LEA-6H used beyond it’s operating conditions in 3DRobotics GPS modules, but I can’t . Also I can’t find any UBlox documentation which point that LEA-6 can be used in such way.
So may be somebody could clarify me about this.
By beyond operating conditions, I mean next:
The LEA-6 datasheet allows a maximum VCC of 3.6 V - this is ensured by the onboard 3.3 V voltage regulator on the interface PCB. But it says also that the maximum voltage on an input pin is VCC. On APM 2.5, the GPS is directly connected to the Atmega 2560 which is powered with 5 V (to be correct: there are small inductors in line with the datalines). As a result of this the RX-pin of the LEA-6 module gets 5 V levels instead of 3.3 V.
Doesn’t this damage the module?
The 5V input goes to a 3.3V regulator (TPS79133DBV) so the Ublox-LEA-6 module is internally powered with 3.3V not 5V.
RogelioN, you are completely right - module is powered correctly by 3.3V, so module VCC is 3.3V.
My perplexity and question is only about RX-pin of the Ublox-LEA-6, which from spec as “Digital IO Pin High level input voltage” or even “Input pin voltage range” must be powered max by VCC. But it connected directly (as I wrote: there are only one small inductors in line with the datalines) from Atmega 2560 pin, which is 5V.
G’day ycherniavsky: That’s a good question (June 4) about exceeding 3.3V on the lea -6H Rx pin. Probably you already have an answer and I hope you post it. Even if the Ublox stands up OK, it would not be good practice. I would interpose one of those little 5V to 3V signal converters that you can get from Sparkfun and others. They are inexpensive and very useful in sending signals up and down between 3V and 5V modules.