FAN5622SX Integrated Circuits (ICs)

LED driver is an important component for controlling and powering light-emitting components in a variety of applications, and FAN5622SX from Fairchild Semiconductor can be classified as a PMIC (Power Management IC) — LED Driver. In this article, the application field and working principle of FAN5622SX will be discussed.

FAN5622SX is a constant-current regulator, ideal for driving high-brightness LEDs. It is a dual-channel design with an internal 0.3 Ohm series pass element, allowing the device to sink up to 1.2A of continuous current. FAN5622SX has adjustable dynamic and static voltages, delivering up to 20V of voltage across the load. As a member of FAN5622 family, it also provides integrated thermal and short-circuit protection.

FAN5622SX operates in two modes, i.e., DC and PWM. In the DC (Direct Current) mode, the FAN5622SX sinks a user-configurable, constant current to drive a load. By setting the dynamic, static and current parameters (with enable pin, voltage and current inputs), the LED can be dimmed and brightened with a myriad of options, eliminating the need for user adjustment of the LED current as the LED is de-rated over time. In PWM (Pulse Width Modulation) mode, the LED current is modulated by a pulse-width-modulated signal on a logic input. The PWM frequency, duty cycle and enable pin provide a wide range of control options.

FAN5622SX is suitable for various automotive applications, such as interior ambient lighting, GPS navigation, instrument cluster, headlight and rear combinations. It is also suitable for multiple other applications, including professional lighting and signage, general illumination and high power LEDs. When used in an automotive environment, the ultra-low 1.2A current and the robust short circuit protection make FAN5622SX the perfect driver for High Brightness LEDs.

The working principle of FAN5622SX can be explained as follows. FAN5622SX uses a voltage-mode control architecture to allow the user to set an accurate constant current level. It has an internal reference voltage of 0.6V, and an accurate current setting that allows the LED current to be adjusted at any voltage level. A voltage-controlled current source pulls the drain of the device to the reference voltage, while the internal reference voltage is the low side of a voltage comparator. The other input of the comparator is a voltage set point connected to the LED, and the voltage-controlled current source pulls the current of the device up to a corresponding level.

In DC mode, the current is set by the user. The negative input of the voltage comparator is connected to the reference voltage, and the positive input is connected to a voltage divider network. The user can set the voltage divider so that the voltage at the positive input of the comparator is proportional to the LED current. The internal current source control circuit then pulls the LED current up to the programmed level.

In the PWM mode, the LED current is modulated by a pulse-width-modulated signal on a logic input. This input has a frequency and duty cycle set by the user to produce the desired current level. The logic output of the PWM signal is connected to the negative input of the voltage comparator, and the positive input of the comparator is connected to the voltage divider network. As the duty cycle of the PWM signal is varied, the voltage of the positive input of comparator follows the voltage divider network, and the internal current source control circuit adjusts the LED current accordingly.

In summary, FAN5622SX is a PMIC — LED Driver offering various application fields and a precise working principle. It is a perfect choice for automotive and other applications, as its accuracy and reliability provide a pleasant user experience.