Teseo-Liv4F pinout confusion

[Ikke]

While researching the GNSS module for my project, I got somewhat confused about the power connection of the LIV4F module due to inconsistent information in the manuals. The general recommendation is to run at 1.8V for optimal power consumption, but my interface is running at 3.3V. In the evaluation board manual (UM3212), there's a 3.3V VCC_IO on pin 7 for communication and 1.8V VCC pin 8 for powering the module which would easily allow this set up. In the hardware manual (UM3004) for the module however, pin 7 is marked as reserved - which means there's no separate VCC_IO and I would need to level shift all the communication channels when running at 1.8V.

I was hoping you could clarify whether pin 7 is available as VCC_IO or not?

[Peter BENSCH · Accepted solution]

Welcome @Ikke, to the community!

Where did you find something about 1.8V, not including UM3212?

In general, the respective data sheets, not user manuals or application notes, are authoritative for the technical data and parameters. The data sheet of the LIV4F only contains the VCC and VBAT voltage ranges of 3.0...3.63V. Pin 7 was actually connected to VCC_IO in some predecessors of this module, but pin 7 is not to be used in the LIV4F.

The switch for VCC (3.3V/1.8V) visible in UM3212 is a remnant of a universal evaluation platform for Teseo-LIVxx, which is why the block diagram (fig. 19) also shows the module designation Teseo-LIV and not Teseo-LIV4F.

In summary, the LIV4F module must be operated with 3.0...3.63V.

Hope that answers your questions?

Regards
/Peter

[Ikke]

Dear Peter,

Thank you, that's what I needed to know!

As for the 1.8v, there's also the reference on page 4 of the hardware manual, which says "To optimize battery current consumption, it is possible to use a SMPS at 1.8 V to supply VCC."

[Peter BENSCH]

Once again: relevant for the parameters of the respective component is always and exclusively its data sheet.

But let's break it down: the UM3004, rev 2 is obviously older (2022-11) than the data sheet, rev 4 (2023-07) (later readers please pay attention: could change in the future). It is very likely that at some point during the development of the LIV4F, it was planned to specify it from 1.8V as well. Then the UM3004 was written, where the talk is about this voltage. But later it turned out that the module cannot be guaranteed to work 100% from 1.8V, so it was specified for 3.3V only - and unfortunately they forgot to take the relevant section out of the UM3004. The first sentence of this post applies again here at the latest.

But one more remark (attention, subjunctive!): even if the 1.8V had been specified, the same voltage would have applied to the IOs. So either level shifters would have been necessary to connect a 3.3V MCU, or the MCU would also have had to run on 1.8V. But as I said, this is all hypothetical, since the specification is 3.3V.