This week, Diodes Inc. introduced a new IC for LEDs in automotive applications.

The AL5814Q is automotive-compliant, AEC-Q100 Grade 1 qualified. It features low dropout voltage and enhanced dimming.

The AL5614Q is an adjustable linear LED controller that works with an input voltage range of 4.5 volts to 60 volts. The device supplies a maximum of 15 mA of drive current and is used with an external LED driving power device, such as a MOSFET or BJT.

 

The AL5814Q LED driver-controller. Image from Diodes Incorporated

 

The employment of an external driving power component minimizes the unit’s internal power dissipation when compared to traditional linear LED drivers. This arrangement also enables the AL5614Q to drive higher current LEDs or multiple LED strings. Because of this, the device is suitable for applications that require higher light output including: 

  • Automotive rear lamps
  • Automotive interior lamps
  • Automotive instrumentation illumination 
  • Automotive position lamps
  • Automotive license plate illumination

As a low dropout voltage device, the unit can operate effectively even when the power supply voltage is very close to the voltage of the output.

 

Pin Assignment

The unit’s output current can be set via the voltage at the VSET pin. This voltage is set through the use of a resistor divider, R5 and R6, operating between the REF pin and the VSET pin.

 

Pin assignments. Image from the AL5814 datasheet

 

The voltage across the external sense resistor, R1, is fed to the FB pin for sensing. When the voltage exceeds VSET voltage that has been set by the voltage divider, the output at the OUT pin goes lower, decreasing the drive to the external transistor. 

The VFAULT pin is responsible for pulse width modulation for dimming and open-LED detection (which can be supported via the SFAULT pin). 

 

Achieving Thermal Fold-Back Behavior

This is done through the use of a negative temperature resistor (NTC) for R6. Then, when the temperature of the detecting point rises, the NTC resistance decreases and makes the voltage at VSET decrease. Consequentially, the output current decreases, preventing the system from overheating.

Additionally, the AL5814Q has internal overtemperature protection (OTP). This is achieved by shutting the IC down when the junction temperature is over +160°C and turning it back on when the junction temperature drops by +30°C.

 

Other Major Specs

  • Available in an MSOP-8EP package
  • Operating temperature range: -40°C to +150°C. 
  • Storage temperature range: -55°C to +150°C.

 

LED Controller Options from Around the Industry

While we’ll still have to wait for self-driving cars and for the widespread adaptation of all-electrically powered cars, the incorporation of electronics into gas-powered and hybrid vehicles proceeds apace. LEDs are replacing incandescent bulbs, and as expected, many manufacturers are offering a wide range of LED driver-controllers, each optimized for its own specific application. Here are two examples:

  • NXP offers the 16-channel PCA9685 LED controller, which is I²C-bus controlled. This particular controller is optimized for RGBA backlighting—each LED output has its own 12-bit resolution (4096 steps) fixed frequency individual PWM controller. Like the AL5814Q, this component allows adjustable brightness.
  • ON Semiconductor has the NCV7691, a device that uses an external NPN bipolar device combined with feedback resistor(s) to regulate a current for use in driving LEDs. This is another controller that's geared towards automotive applications.

 

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