This P-MOSFET can also be used in a soft-start circuit:



This circuit should only be used for the supply voltage of LEDs, because you will always have a voltage drop across source drain channel. If you plan to use this circuit with digital 5V supply then much less than 2A should flow through the P-MOSFET, resulting in a voltage drop of less than 2A x 0.025Ohm = 0.05V.

The above circuit should be put on each 32 x 32 matrix modul to provide a local soft-start of Uled. With 200mA x 32 = 6.4A per column less than 6.4A x 0.025Ohm = 0.16V will drop across source drain channel, resulting in a heat dissipation of about 1W. Nevertheless, I would recommend to use a heatsink, because in the moment of soft-start heat dissipation can be quite high, depending on actual load situation behind the soft-start circuit. It's wise to have all LED drivers turned-off at this moment, so that only into the decoupling caps supply current will flow. This will tremendeously decrease heat dissipation at the moment of soft-start.

Even if you plan to use 5V also for the LED circuitry, you should in any case provide different supplies for the digital circuitry and the LED circuitry, even if this might complicate a bit the column driver section. The reason is, that supply voltage of LED circuitry will show an awfull ripple noise, which cannot be relevantly filtered, unless you want to use sophisticated LC-filters!

Kai