Auto Electronics

STMicro chip consolidates door-mounted drivers

STMicroelectronics has introduced the L99DZ70XP, a single-chip driver IC that can replace the discrete drivers otherwise mounted in multiple locations inside a vehicle door. The device produces the major signals required to drive vehicle door-mounted systems and also provides an improved method for controlling electrochrome rear-view mirrors, the company said. The L99DZ70XP allows compact, integrated door-zone controllers that are easier to fit and offer greater long-term reliability.

Mirror functions that can be controlled by the new device include motor-driven door-mirror adjustment, powered folding when the vehicle is parked, a heater for automatic defrosting, and electrochrome dimming to enhance night-time driving comfort.

Other applications include motor-driven locks and deadlocks, and lighting features including interior orientation lighting, such as footwell lights, and functional lighting, such as safety lights or turn indicators. Such lighting circuits require different lamp-driving characteristics depending on whether LEDs or conventional bulbs are used. By consolidating all the driver circuits on a single chip, the L99DZ70XP saves design and mounting of multiple individual assemblies, reducing cost and time to market as well as saving space. By eliminating many connections and potential failure points, the chip also increases field reliability.

Conventional EC controllers typically use a regulator that requires a high-power external resistor, but the L99DZ70XP generates control signals for a small external MOSFET driving the EC element, saving space and cost and allowing closed-loop current control for enhanced reliability.

Six of the L99DZ70XP outputs are optimized for motor-drive applications. As many as four are available for lighting applications, and two of these can be programmed to drive either LEDs or conventional bulbs. Another output is optimized to drive the mirror defroster. Each of the drivers uses pulse-width modulation for accurate current control.

Other capabilities include soft starting for loads such as motors or bulbs, to prevent high initial currents causing potentially damaging surges within the vehicle wiring. The L99DZ70XP uses serial communications over an industry-standard SPI link to exchange information with the host controller, including diagnostic information for each output to aid fault-finding and repair.

The L99DZ70XP joins ST’s Door Zone family of integrated drivers, which features seven other devices for driver-side, front-passenger and rear-passenger doors. The L99DZ70 is qualified to automotive standards and delivered in a 36-pin PowerSSO-36 package with enhanced thermal properties for high reliability in all automotive operating environments. Samples are available immediately, with volume production scheduled for Q1 2009 at $3 for 100,000 pieces.

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