Simple UART voltage level translator

This is a very simple, small, symmetric, two-channel (one channel in each direction) voltage level shifter, using two 74LVC1T45 chips in SOT-26.  At JLCPCB or LCSC, look for 74LVC1T45W6-7.  Either side provides their own logic level supply, which can be anywhere between 1.65 V and 5.5 V.  For example, if one side is powered by a battery whose voltage varies, this lets you safely interface to a 3.3V or 5V MCU or USB-UART adapter.

The ground is shared: both sides must connect to the same ground.  This is not an isolator.

Here is a 3D rendering of the board itself, so you can get a better picture of its size:

The pads on either side are standard through-hole pads with 0.1" or 2.54mm spacing.  The board is square, and the distance between the two pad rows is exactly 0.4" or 4×2.54mm = 10.16mm.