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Automotive-Grade Backlight LED Driver is Optimized for LCD Panels

The chip, developed by ROHM, is compatible with 3- to 12-in. vehicle LCDs, enabling common control board designs.

Typically, a new car today offers sharp liquid-crystal display (LCD) screens that help drivers navigate, keeps them up-to-date on their vehicle’s performance, and provides entertainment. Automotive displays, particularly the center stack and the instrument cluster, are commonly based on thin-film-transistor (TFT) LCD technology. Many cars already have six or more displays when you add in the smart back mirror, head-up display (HUD), rear-seat mount on the head support, and rear-seat mount on the roof.

And like the TV screens inside homes and offices, automotive displays are getting bigger and delivering higher resolution. Providing such display performance requires a greater number of high-brightness LEDs for backlighting, as well as LED drivers featuring multichannel operation and advanced dimming features that can prevent flicker effects.

ROHM’s latest LED driver IC, the BD81A76EFV-M, is designed for high-illumination LCD backlighting in automotive instrument clusters, center information displays, and car navigation. Unlike conventional drivers with four channels that support LCDs up to 8 in., incorporating a constant-current driver with low heat generation enables this IC to provide six channels of output in one chip. Each channel can draw up to 120-mA (max) output and support LCD panels in the 10- to 12-in. class. It also is able to withstand high input voltage (maximum 35 V).

In contrast to conventional six-channel backlight LED drivers utilizing only boost control, a buck-boost current-mode dc-dc converter is built in to enable stable operation during power voltage fluctuation. Buck-boost control ensures compatibility with both small and large LCDs using a single driver.

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In addition to providing compatibility with both small and large LCDs, adding a buck-boost current-mode dc-dc converter helps to achieve stable operation during power voltage fluctuation.

While LED drivers often are only capable of driving 36 to 60 LEDs (6 to 10 LEDs/channel), ROHM’s new driver IC expands the range from 6 to 60 LEDs (1 to 10 LEDs/channel). This further ensures the support of not only larger displays, but also small- and medium-size panels using a single driver. As a result, it’s able to contribute to a common design of the control board for conventional panels, along with the latest large-size displays.

What’s more, ROHM’s original pulse-width-modulation (PWM) dimming technology (patent no. 2018-169705) provides a dimming ratio of 10,000:1 (@100 Hz), improving visibility and giving engineers greater design flexibility for center information displays and instrument clusters.

ROHM puts standby current consumption at just 10 µA. This reduces power consumption to less than one-third that of functionally equivalent products featuring a standby current of 40 µA (typ.), according to the company.

Protection features include:

  • Undervoltage lockout
  • Thermal shutdown
  • Overvoltage and overcurrent protection
  • Short-circuit protection
  • LED open protection
  • LED short protection
  • PWM low interval detect

In addition to obtaining qualification under the international AEC-Q100 standard for automotive reliability, the BD81A76EFV-M integrates a spread-spectrum function as a countermeasure against EMI that allows it to clear CISPR25 noise requirements for vehicle applications. This results in stable operation in automotive systems sensitive to noise.

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