Designing for Real-time Reliability 

Automotive instrument clusters display mission-critical data for safe operation, ranging from the status of vehicle systems to driving conditions. These dashboard data centers can be as simple as a series of gauges or as complex as hybrid 2D and 3D systems.

Instrument clusters enable communication between driver and machine using an interface fitted into the dashboard to showcase a myriad of crucial metrics to the driver. The interfaces and the metrics they display will vary by vehicle, and likely include:

• Speedometer - how fast the vehicle is currently driving
• Tachometer - the engine’s revolutions per minute (RPMs) 
• Odometer - lifetime mileage of the vehicle to date
• Fuel gauge - how much gas is left in the tank
• Trip odometer - distance from Point A to Point B
• Temperature gauge - current temp of engine’s coolant
• Warning lights - alarms for issues with engine temperature, oil levels, tire pressure, airbags, anti-lock brakes, engine, seatbelt, or battery
• Indicator lights - status indication for turn signals, driving gear, and more

Additional data that may be included in some instrument clusters:

• Miles per gallon/fuel economy - current MPG rating
• Remaining driving range - how long before the vehicle needs to refuel or recharge
• Clock - current time displayed on the dashboard
• Temperature - current outdoor temperature

How do instrument clusters work?

Dashboards or instrument clusters are made up of several switch inputs and sensors for various functions. These inputs, such as the tachometer, fuel gauge, odometer, temperature, speedometer, and other parameters are connected to a multiplexer (MUX), which provides inputs to the processor/controller. 

As the brains of the operation, the controller processes these inputs and then utilizes LED drivers, load drivers, motor drivers, stepper motors, and audio DAC to transmit data to the dashboard featuring a series of indicators, backlit LED screens, and illuminated gauges.

CAN and LIN transceivers enable connectivity to help protect the device from ESD or overvoltage. 

A wiring harness connects the instrument cluster to the electronic control unit (ECU) or controller.

All of these functions must take place in real time to maintain driver safety.

Automotive Instrument Panel Block Diagram

Engineering Tips

• Power Management TVS - reverse working maximum voltage (VRWM) should be higher than the supply voltage (V supply)
• Power Management Schottky Barrier Rectifier - at minimum, you need twice the output voltage of the switch-mode power supply (SMPS)
• Output Drivers - the drain-source voltage (VDS) must be at least twice the V supply

Design Considerations

• Efficient power management - minimizing losses and enhancing efficiency is essential for all components powered by the vehicle’s battery, including the instrument cluster
• Reliability in harsh conditions - designs must be able to withstand a range of operating conditions commonly found in auto applications
• ESD/EMI protection - ensuring there are no disruptions from electrostatic discharge and electromagnetic interference is crucial for safe, reliable operation 

• Surge protection - safeguards need to be in place to suppress transients and prevent overvoltage

• Fast switching - instrument clusters require fast and frequent switching and need components that can keep up without compromising speed or efficiency

• Low forward voltage drop - maximizing efficiency is important for the instrument cluster and other automotive devices

• Thermal stability/heat dissipation - optimal thermal performance is needed for safety and efficiency

• Applicable industry standards - for auto applications, components must adhere to stringent requirements, including AEC-Q101 qualification

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