This A6269 automotive LED driver array circuit is designed by Allegro MicroSystems and can be used in automotive application using a 12 or 24 volts power supply.
The toggle action of the SW input will be reset to off at each power-up. From this stage, applying an EN = high signal turns the LED on, and an EN = low turns the LED off.
When power is applied (with EN connected to VIN), there will be a short startup delay, tON , before the current starts to rise. The rise time of the current will be limited by the internal current slew rate control.
This circuit use a manual switch to toggle the light on or off. While the light is in the off state, the central lighting control unit may send a PWM signal to dim the light gradually before turning off completely. The interaction of the two control inputs is explained below:
• Internal flip-flop (hence LED light) starts from off state, ensured by power-on reset.
• The light can be turned on by either EN = high or by a momentary toggle (high-low-high) at the SW input.
• If the light is initially turned on by EN = high, it can be turned off by EN = low. This allows PWM dimming of the light.
• If the light is initially turned on by SW input, it stays on regardless of the state of EN. The light goes off only when another
momentary toggle is received at the SW input, or when the power is removed.
The behavior above is graphically explained and represented by Allegro MicroSystems using the state diagram bellow.
THTH Sets the thermal monitor threshold, TJM , where the output current starts to reduce with increasing temperature. Connecting THTH directly to GND will disable the thermal monitor function (see datasheet).
Rref = K/ILAx ; wh ere K is 30 and ILAx (nominal output current at each Lax)