GPS supply filtering

[giszo]

I have a project where a switching regulator is used to provided the main 5V supply for the whole system where a GPS module is also included.

My main problem is that the GPS module is unable to find any GPS fix or satellites at all. Unfortunately I have no access to expensive hardware (oscilloscope, etc.) to make further debugging on this issue, but my first bet is the noise of the switching power supply. What kind of filtering could I put in front of the GPS module to eliminate the noise generated by the switching regulator?

Regarding the type of the regulator, I have tried both LM2576 and LT1376. If I remember correctly the LM runs at 52kHz and the LT is at 500kHz. In long term the LT would suit my needs better because it allows the supply to be build with smaller components.

 

[Surendhar M]

You just follow the datasheet of LM2576 regulator for the filter design. It will give you the required voltage and the level noise will not be huge factor in the digital circuit design. Moreover I just want to know how the GPS device is interfaced? Is it connected with the microcontroller?

 

[ravindragudi]

I guess with whatever the SMPS IC you are using, the output capacitor should be able to help you to better extent on limiting the noise in supply. The reason for not tracking any satellite may not be directly related to the SMPS circuit I believe. It will be somewhere else.
Check if you have any metallic objects/ shields covering the GPS IC and the connecting antenna. If so, do away with these metallic objects and shields from the way of getting the signal from the satellites to the GPS IC, antenna.
Do the trial in an open area where you can see a better satellite signals on other reference GPS devices. Then try playing with the GPS antenna position to get some sort of satellite signalling in your proto.

 

[giszo]

You just follow the datasheet of LM2576 regulator for the filter design. It will give you the required voltage and the level noise will not be huge factor in the digital circuit design.

Yes, both supply PCBs were designed according to the recommendations of the datasheets.

Moreover I just want to know how the GPS device is interfaced? Is it connected with the microcontroller?

The GPS device is currently interfaced with an ARM microcontroller.

I guess with whatever the SMPS IC you are using, the output capacitor should be able to help you to better extent on limiting the noise in supply. The reason for not tracking any satellite may not be directly related to the SMPS circuit I believe. It will be somewhere else.
Check if you have any metallic objects/ shields covering the GPS IC and the connecting antenna. If so, do away with these metallic objects and shields from the way of getting the signal from the satellites to the GPS IC, antenna.
Do the trial in an open area where you can see a better satellite signals on other reference GPS devices. Then try playing with the GPS antenna position to get some sort of satellite signalling in your proto.

Actually the exact same GPS receiver works fine when the microcontroller and the GPS receiver is powered from the USB port of my notebook. That is the reason why I started to think that something is wrong with my custom board.

 

[Surendhar M]

Check for the voltage levels of the regulator in the working mode. Monitor for any drop in the actual voltage level.