Reasons for a full custom development:
- Has to fit into available space
- Integrate external conditioning circuits
- Complex electronics with FPGAs, DSPs
- High power or high temperature
- High quantity (Save on unused components)
- Special look, design, haptics
Full Custom

Special tasks require special solutions. A control unit might have to fit into a small space or even be an integral part of a tool. Or it makes sense to integrate external load drivers or sensor conditioning circuity with the controller.
Or there is a task unique enough to fit into no category in off the shelf equipment - like in this rugged digital motor controller for BLDC motors up to 8kW, developed 1995 for Andras Steuerungssysteme GmbH in Bremen. It's a bit of everything: Integration of FP DSP to compute the PWM, a special analog preprocessing to get 2 million steps from one revolution of a position encoder and the problem to get the heat out from the 1200V IGBT module and the braking resistor in a waterproof enclosure.