Automakers have been gradually switching to LED lighting for automotive headlamps because of LED features such as high efficiency and long service-life. In addition, the applications of LED-driven DRLs (Daylight Running Lights) to vehicles is spreading mainly in Europe from a safety perspective.

Automakers have been gradually switching to LEDs for headlamps and DRLs (Daytime Running Lights), primarily due to the many advantages that LEDs provide, such as high efficiency and long service life. The adoption of LED DRLs in particular is quickly spreading, especially in Europe, as manufacturers focus on safety.
ROHM's new dedicated LED driver IC (BD8381EFV-M) includes all functions required for LED headlamp switching (high/low) and DRL operation. A step-down DC/DC converter is built in that supports a variety of LED configurations, along with a PWM dimming function required for DRLs, enabling control without a microcontroller. In addition, multiple protection circuits are incorporated, including open/short detection, ensuring a high degree of reliability while reducing the number of external parts.

• Input voltage range : 5V to 30V
• Voltage accuracy±5% (Ta=-40ºC to 125ºC)
• Built-in step-up/step-down current mode DC/DC controller
• External mounting supports step-down, step-up, and step-up/step-down applications.

• Compatible with DRLs (Daylight Running Lights)
• Oscillator built-in for PWM dimming
• Supports linear dimming
• Multiple protection circuits (overvoltage, overcurrent, thermal shutdown, undervoltage lock out, LED anode/cathode ground protection)
• Integrated LED open/short detection
• Compact HTSSOP-B28 package

The number of LEDs used in headlamps and DRLs can vary significantly based on set design and application requirements. With this in mind, ROHM includes a DC/DC converter that supports boost and buck operations for increased flexibility.

DRLs normally operate at full brightness during the daytime and then dim at night when used in combination with the headlamps. ROHM's LED driver ICs integrate a PWM oscillator circuit that enables PWM dimming operation without a microcontroller while preventing changes in hue. The oscillation frequency can be set via external resistor/capacitor circuit.

ROHM LED driver ICs feature an overcurrent/ground protection function that detects the current flowing to the high-side MOS switch, enabling short/ground detection not only in the LED lamps, but in the boost/buck application circuit as well. High accuracy detection is performed through a resistance balance circuit connected in parallel to the LED circuit. This protection circuit will output a flag and alert the system in the event of LED failure.

Dimming via DC voltage is possible in addition to PWM. This allows dimming to be performed based on the temperature of the LEDs by using the input from a thermistor and temperature sensor situated near the LED lamps, preventing LED degradation.