Electronic – PCB Matrix Touchpad

I expect the high-resolution display to use slightly more, but roughly the same amount of power as the lower-resolution display.

Most of the power consumed by the display in a tablet like this goes to two primary components: the backlight and the LCD.

Typically the backlight consumes very roughly 75% of the energy going to the screen. Most tablets like this one have a CCFL tube backlight; some of them have a "white LED" backlight. It doesn't change the answer for this question -- given either kind of backlight, that backlight will consume exactly the same amount of power no matter what LCD is placed in front of it. Turning the "brightness" down can save a significant amount of energy.

As you probably already know, the "liquid crystal display" (LCD) such as the ones in the tablets you mention act as shutters -- they either let the light through, or they block the light, or something in-between. They typically consume the other 25% or so of the energy going to the screen.

Some of that energy goes to keeping the liquid crystals "open" (or "closed"). A cluster of 4 pixels requires exactly the same power to keep the liquid crystals "open" (or to keep "closed") as a single pixel 4 times the size.

Some of that energy is lost due to parasitic capacitance of the INO transparent "wires" on the screen. The total row capacitance and the total column capacitance is about the same for the two screens, so the amount of energy required to update a row (charging and discharging every column line across the entire screen) is the same. However, the higher-resolution screen has more rows to update, so assuming the same full-screen update rate, it requires more power.

As a side effect of the screen having a higher resultion, the CPU and the CPU-to-display bus will have to do a little more work dealing with more pixels.

So the things that use up the most power use exactly the same amount of power no matter what the resolution. There are a few things that require more energy for the higher-resolution screen. So I expect the high-resolution display to use slightly more, but roughly the same amount of power as the lower-resolution display.

For short traces, ringing is caused by parasitic inductance / capacitance effects. For long traces, it can be caused by impedance mismatch / reflection or parasitic inductance / capacitance effects, or both. For digital signals, a trace is long if the round-trip propagation time to the load and back to the source is around the same as the signal rise time. For sine waves, a trace is long if the round trip time is, let's say equal to or greater than the period / 8. Some people might use a number other than 8, which is fine. Arguing over the exact number is not really the point.

In theory, if the source is terminated in the characteristic impedance of the line, no damping would be needed, even if the source impedance does not match the load impedance. In practice, damping is sometimes needed, especially on long traces, so it is best to put it in there. You can start with 0 Ohms if you don't think it is needed. Sometime people refer to a series damping resistor as being a load matching resistor. But usually that is not the case. It is really just for damping. In order for it to help with load matching, you would need to have a terminated load, and most loads in digital circuits are not terminated (except for some very high-speed stuff, and some differential stuff, e.g., LVDS).

One other way to get ringing is in an amplifier with feedback. This could include audio amplifiers or error amplifiers in regulators. That could be caused by bad PCB layout in some cases if there is unintended feedback to a sensitive node (usually due to capacitive coupling from one trace to another trace or pad).