I'm trying to drive a 3.3V IC from an Arduino which has 5V logic pins, so I need to shift that 5V down. There's no data from the 3.3V device to the Arduino so I don't need to shift back up.
Can I use a voltage divider to do this? My concern is that since the device is not a passive component (it's an ST7735 LCD driver), its effective resistance is not constant (right? As the transistors and whatnot in the IC switch, the overall resistance/current will change?) and so the voltage "output" from the divider will change.
That is, in this picture:
R2 is not constant and so Vout may vary.
Since Sparkfun's logic level converter uses a voltage divider for down-shift, I suspect that this is fine, but I don't understand why.
(This is my first electronics project. I would usually just use Sparkfun's LLC but I'm in a country where it's not so easy to buy electronics from America!)
I should clarify that I'm not using this 3.3V to drive the LCD itself (I think). The breakout has a separate VCC pin, which I'm connecting to a 3.3V supply which the Arduino provides. It's just the logic pins I want to shift.