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Teseo-LIV3F: max current out of VCC RF pin?

GChri.2
Associate

I'm considering the Teseo-LIV3F(L) for my current project, but I could not find an Abs. Max Rating for the current through VCC RF. The closest to this rating I could find is Fig. 10 in the LIV3F hardware spec that mentions a TPS22943, which limits its output current to 40mA - 80mA.

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2 REPLIES 2

Limited by the inductors acting like fuses, say the wattage/size of the 27nH you have there externally.

The real killer in these applications is a short as you're fumbling with the antenna connection, or the technician installed a lightening arrester that looks like a short at DC frequency. Or someone drives a nail/staple thru the coax.

Many modern GNSS antenna are in the 10-15 mA, range 35-40 mA likely the outliers. Most likely only need around 2.5V to run their LNAs

The feed-thru from VCC is going to give you a hard ceiling. Need enough to run the receiver, and power the antenna. I seriously doubt the internal inductor is rated more than 250mW. If you need something more beefy, route your own VIN to the TPS22943 via a suitably rated inductor, directly from VCC.

Now VCC_RF is used where you don't want you're own supply, and the RF_IN doesn't want to see things other than VCC. It may or may not have a DC blocking capacitor in-board.

If you were working with 5V or 12V antenna systems I think you'd definitely want a blocking capacitor.

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GChri.2
Associate
The feed-thru from VCC is going to give you a hard ceiling. 

correct.

unless someone tears down a module and inspects the filter (or someone from ST replies), I think it is best to assume that the abs. max. is >= 80mA, which is the upper limit of the TPS22943's specified current limit range.