I've got a synchronous LCD that is rated at 60Hz but I'd like to run it at either 45Hz or 30Hz to save power/memory bandwidth. My concern is that this will affect the contrast ratio of the display, as well as possibly the life expectancy. Does anyone have any insight on the dangers of running your LCD at a refresh rate lower than it was rated?
Most are rated at 60Hz or higher but will work at lower rates, I have driven several at 50Hz. Often the 60Hz is the typical for PC display.
I do assume you mean a graphics LCD not a monochrome alphanumeric one.
The only way of effecting the contrast ratio is if the LCD, were to change its pixel setting to more white, that you can only tell by trying various LCDs at 30 and 60 Hz.
Possibly looking at STN instead of TFT.
Anyway you will have a lot more power being used by backlights for most TFT graphics LCDs.
Not seen any myself, but I have not driven as low as 30Hz.
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I have considered this a while ago for similar reasons, not memory bandwidth but serial interface throughput (could/can make an SVGA 16 bpp directly from system memory of a SOC using DMA, at a max. of 16 MHz pixel rate). I have seen TFT modules which specify only maximum hsync and vsync frequencies, meaning they will get in sync allright. I have done that myself on TFTs I have worked with, they did tolerate very low frequencies - I am sure I tried one at 16 MHz (SVGA, many years ago). What may degrade is the contrast - perhaps you also have seen how the TFT goes rainbow colours when the signal is gone. Now how those TFT gate caps discharge etc. is not common knowledge, I once tried to locate some info and did not get anything conclusive. Trying things out may well be worth it - if you can guarantee the same TFT will be used in the product lifetime, that is (buying a lifetime supply may be the only way to do that).
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