I got a Graphic ST7565 Negative LCD and a RGB backlight negative LCD 16x2 that I'm trying to hook up to an ATMega644p (avr-gcc). Everything is working great however I just tried to enable PWM control of the LED backlights. I have the backlights of both displays connected to the same pins (PB3, PD6, and PD7). The RGB wires for the GLCD are going thru 150 ohm resistors and the RGB wires for the char LCD are going straight to the display (Built in resistors). When enabling PWM both backlights started acting real funny. I never got any dimming, usually the backlight wouldn't come on at all, and when I could get the backlight to come on (with the same settings on all three channels) the red would not light.
After researching on the web and talking to people in chat rooms I believe my problem is that the avr can not provide enough power for all the backlights. To verify that I disconnected the backlights and put in a single RGB LED. The LED acted perfect, I was able to dim each channel individually and everything. So my question is, does anyone know a good driver chip to power the backlights with? Or (bare in mind I am very new to building circuits) it seems to me that driving these LEDs could be done with just a few components such as some transistors and a few support parts. If that sounds possible can anyone suggest what I might call such a circuit to search for examples on the web.
Thank you in advance and Thanks to everyone at Adafruit for making such a great resource for beginners.