Taking aim at upscale vehicles, which have many features squeezed into their doors, STMicroelectronics has unveiled a chip that eliminates the electromechanical relays now used for window control. The door-zone driver can drive power devices that replace relays, saving space and reducing noise while also lowering the overall cost of a door subsystem.
The driver for actuators highlights the growing trend toward digitization of high-power functions such as motors. ST’s L99DZ80 embeds a slew-rate control function, which can drive four external MOSFETs that work with electric window motors driven via pulse width modulation (PWM)—instead of using bulky relays.
Eliminating the relays that now drive the electric-window motors can cut component costs. The combination of MOSFETs and PWM drivers also reduces the noise caused by relays.
“Having control for MOSFETs lets window lifts perform soft landings, which reduces force on the glass,” said Giovanni Torrisi, Technical Marketing Section Manager for STMicroelectronics’ Body and Audio Division. “A Serial Peripheral Interface (SPI) controller lets you manage the slope of the signal, which lets you get better electromagnetic coupling performance without the cost of EMC protection needed with relay-based systems.”
The multifunctional device can also drive many other functions including double door-lock control, mirror fold, and mirror-axis control, a mirror defroster, bulbs, and LEDs. The power device also integrates a control block with an external MOS transistor for charging and discharging of electrochromic (dimmable) mirror glass.
Torrisi said the device has already been selected by an unnamed German carmaker. Door electronics are a major market for ST, which has shipped over 100 million door-actuator devices in the past decade.