AR Display Form Factor Board
Form factor board designed for a client to drive an LVDS LCOS with a MIPI signal from an external board.
Features:
Small dense layout, 40mm x 20mm
6-layer board with impedance matched differential signals
Integrated LED backlight controller
Layout
Schematic captured from development board design which I had performed physical validation on previously. Small DC-DC power supply added to reduce number of connections to carrier board. Very dense layout required with several mechanical clearance requirements.
Display Configuration Issues
The configuration of the MIPI to LVDS conversion chip was not correct and required some work with the vendor to address. Originally, the issue was hypothesized to be caused by the use of a non-standard backlight configuration. Any delay in the backlight timing could potentially cause a shift in the perceived brightness of each color, RGB, since the blanking (inverse image) of the display occurs when the backlight is off. A timing timing analysis of the delay was done with an oscilloscope and determined to be well within bounds. Eventually it was discovered that a register configuration set from a legacy product was incorrectly set for our application and the changed fixed the visual distortion.
Integrating and Validating
Other than the display configuration issue, the board performed as expected. Firmware written on the main processor controls the remote backlight driver requiring a continuous updating for user defined and ambient adaptive brightness. Future plans for color calibration and temperature calibration of the LED backlight are in the pipeline.
