Analyzing the uBlox LEA-M8T hardware

Hello all,

these days I am playing with a multiconstellation GNSS receiver, concretely the LEA-M8T from uBlox. When I integrate any hardware module into my system I usually look what is inside.

For their modules uBlox integrates the different subsystems into a single silicon device so it is not possible to make a deep analysis on the module, but some common sections can be identified.

 

The two main elements are easily appreaciated. The M8030-KA automotive grade SoC and a 16 MB dual/quad SPI NOR flash memory from Winbond containing the system firmware.

At the bottom right we can identify a 26 MHz TXCO oscillator for the RF synthesizer, with a noise guard ring and rounded by VIAs to GND with its decoupling cap outside the ring. Beside the oscillator we see an RTC Crystal for the core.

At the bottom left we have some antenna short detection circuitry.

Below the memory we can see the core supply ferrite-C filter connected to the output of the onchip DCDC. I appreciated that VCC and VCC_OUT pins of the module are exactly the same!! connected by a direct track!! Looking at the datasheet, the only note about VCC_OUT is to leave it open if not used. Curiously the external VCC is used to supply (decoupled) the NOR memory.
More decoupling caps on top and left to the uBlox SoC.
A C-ferrite-C pi filter at the RF output voltage.

The RF path is clear on the design, coming out from the 40th pin, a matching network formed by inductor, parallel cap and series cap, a SAW filter?, a DC blocking cap and the DC adding LC low pass filter.

Curiously they did not take too much care about the USB differential pair as they cross one VIA far away from the other. On the other hand the UART RX, TX pins were routed together. It is true that the module is tiny and there are not too much length but it is costless to do it right.

 

 

About the PCB technology, they used buried VIAs technology with VIA-on-pad and probably a 4 layer stackup (signal | GND | signal & PWR | GND).

Hope you may find the analysis useful and interesting. Do not hesitate about adding your comments.

 

See you in other analysis ;)