The latest generation of cars offers increased features in comfort and convenience. These features enrich the electronics of dome and door-zone controls, heating, ventilating and air conditioning (HVAC) systems, and wiper, seat and lighting controls.

In automotive comfort electronics, door-zone modules have emerged as viable solutions. A typical module is responsible for controlling power windows, exterior mirrors, door locks, footwell/ exterior lamps and side-turn indicators.

These modules also include power-management functionality and a transceiver - the latter is basically needed to "wake-up" the module, for identification of the key from the ignition lock and for general diagnostic communication.

Figure 1. For rear door electronics, LIN is taking center stage.

The transceiver can be a CAN or LIN according to cost and technical requirements. Due to increased speed requirements, control and diagnosis complexity, the CAN (either high-speed or body) is often used for the front door. For rear-door electronics, there is a clear trend toward LIN as the scope of functions is significantly reduced. Module costs are also reduced with the use of LIN.

The door area is tight and space constraints are demanding. The door compartment is subject to strong vibrations, and is narrow and not easily accessed by assembly plant workers.

Moreover, the wire-harness bundle that can be routed to the door must be limited, since the door is separate from the vehicle body. In spite of these limitations, the number of features is constantly increasing; these constraints are even more demanding if the mirror is taken into consideration.

To reduce costs, implementations of specific functions for door modules need to be flexible and tailored to specific customer specifications.

The L9950 actuator driver controls mirror adjust and fold-in/ out, as well as an advanced lock system, driving the door latch and dead-bolt motor. Five intrinsic high-side drivers are available to control loads such as incandescent lamps, LEDs and the mirror defroster.

Sophisticated diagnostic algorithms allow digital and analog load status to be monitored by reading out folder, lock motor and defroster information, and to react accordingly. Status of all loads is accessible via standard SPI and a programmable current monitor output.

All revved up
Special care must be taken in optimizing current absorption of the modules, especially when the car is not running. Even if current voltage regulators offer very low quiescent current and latest generation bipolar-CMOS-DMOS (BCD) devices are optimized for low power consumption, the