I never really asked myself this question until I ended up in need for current source IC because I want to drive a HDSP-2000 LED display (more or less museum piece
similar was featured on eevblog youtube channel not so long ago) you can find a
datasheet here. Basically it's plain stupid array of LED's with shift register ONLY for cathodes, aka all column anodes are wired together and exposed as 5 pins .. in high brightness each this pin can sink like 20-30 mA, so 5 pins and total can be 100 mA per display, and mul. it by 3+ displays - viola we have half an amp!
Because I'm lazy and don't want to spend 5 pins of MCU with a buffer array IC in between, I was looking for something like serial interface + current sources in one IC, but almost everything I found was serial + current sinks! Like this one:
So I was thinking, why is that? Is making high power NMOS is that much easier/cheaper than PMOS? Or is there something else? Or is it just basic pragmatic practicality of IC companies?
PS. Is there non-obscure i2c + current source IC out there?