Design considerations for LED strip PWM dimming

A note on my background: I'm a programmer in an electronic design company, starting out with hobby projects.

I'm planning to design a PWM LED strip dimmer and colour controller for an RGB/RGBW led strip (yes, this is a hobby project). Before I start picking parts and drawing the schematics I want to ask if I'm not missing anything.

Led strip

A common anode configuration. The LED strip will be up to 5m in length, with 14.4W/m for RGB or 18W/m for RGBW - that's up to 90W, or 7.5A drawn from a 12V power supply. With some overhead it comes out to a nice 3A per channel.

PWM and MCU

PWM switching frequency will be around 6kHz, everything will be controlled by an MCU (STM32F0 family).

Power supply

1. A 12V one with sufficient power, most likely a modified ATX PSU or a dedicated LED one


2. To make sure the PSU handles large switched load well there will be a few large electrolytic capacitors - most likely on the order of a few millifarads, rated for at least 25V with low ESR



3. Inrush current protection - an NTC


4. The MCU will be powered with an LDO, it has undervoltage protection so it will not boot until the logic supply is in it's operating range


5. The 12V rail will be monitored by the MCU and it will only turn on the LEDs if supply voltage is ok


6. According to an online calculator using 35um copper I will make the traces at least 12.5mm wide for common power (anode and current return) and 1.5mm wide between cathodes and drains

Driving the LEDs

1. Low side switched with a single NMOS per channel, Rdson under 20 mOhm


2. To keep Rdson in spec the MOSFETs will be driven using a dedicated driver, like the MCP14A0153, supplied by 12V


3. With 200mW power dissipated in transistors with a larger package (DPAK or Nexperia's LFPAK56) it should not be a concern

PWM

1. As per an article on Digikey I plan to have a frequenct of roughly 6kHz


2. The MCU will run with a 48Mhz clock which is available to the PWM peripheral, giving 13 bits of resolution - probably more then enough

1. Protection - overvoltage and overcurrent, do I need it and how to implement it


2. ESD protection on the terminals



3. Any (magic to me) effects like parasitics, inductance, ringing and what not


4. The relationship between the emitted light and PWM duty cycle is almost linear. What is the relationship between emitted light and perceived brightness?

Apart from the points I listed is there anything more I need to consider? Also I will be grateful for any comments regarding the points above.

I've noticed from comments and @Tony's answer that I should underline that the strip is a ready-made one - I'm not in control of it's schematic. It is a stock one with resistor-limited LEDs in parallel made to use with 12V source, like this one, schematic from Adafruit below. From what I understand you cannot use constant current dimmers with such a setup.