How Automotive Displays can meet Functional Safety: Page 5 of 7

March 13, 2019 //By Szukang Hsien, Maxim Integrated
How Automotive Displays can meet Functional Safety
Functional safety requirements have long been on the radar for automotive systems like braking and steering. Since vehicle displays now show critical information like speed and blind spot views, they also must be functionally safe to protect everyone inside and around the car. What does it take to design a functionally safe vehicle display?

Now, let’s turn our attention the LED backlighting driver. Figure 5 depicts a diagram of typical application circuitry for an LED driver. Here, the input is connected directly to the car battery, which has voltage protection when the output is short. The output can either be a boost or single-ended primary-inductor converter (SEPIC), depending on the number of LEDs per string. I2C and a fault pin are needed to communicate with the MCU.

Figure 5: LED driver typical application circuitry

To achieve ASIL B compliance, the LED driver would need to have these features, as shown in Figure 6:

  • I2C (the data signal and the clock signal) and fault pin to perform setting adjustments and diagnostics on each rail
  • Open or short LED per string detection
  • Output voltage measurement
  • LED current measurement per string
  • Internal resistors with fixed output or adjustable output through I2C
  • Open enable
  • Redundant reference to monitor the output
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