L86, L76 operation at 3.3V I/O?

IoT Modules GNSS Module
1

Hello,
Reading the datasheets, it appears L86 and L76 GNSS modules have absolute limits for the signal IO pins specified as 3.1V:

image
image767×769 24.9 KB

In an example circuit, it is suggested to use a voltage divider to interface 3.3V signaling to the 2.8V nominal input.

However, with a logic level UART, idle level signal is a high level, which results in current leakage through the resistor divider during idle time. This is a power waste for power-sensitive designs.

In a few places, I seem to see comments that suggest that 3.3V is an acceptable input signal level, despite the absolute limit specified in the datasheets.

The L76 EVB schematic, for example, connects the GNSS module to a USB transceiver or to a RS232 transceiver, both of which are expected to exceed Vih absolute limits.

What is the official recommendation/policy on this?

2

Because your forum limits the links and images in the post, here are additional details in a reply comment.

The example circuit I am referencing is at (https://forums.quectel.com/uploads/short-url/tsMfzmPyPhpTMf4lruBQWILBFM5.pdf) :

image
image575×437 17 KB

3

The L76 EVB schematic: (L76 EVB Schematics)

4

Hi Joseph，

The absolute maximum rating (3.1V) for the signal I/O pins on Quectel L76/L86 GNSS modules is a hard limit for long-term reliability, but 3.3V logic can often work in practice. We still suggest staying within the limit to ensure the module’s long-term performance.

BR,
June