STCS2ASPR

The STMicroelectronics STCS2ASPR is a BiCMOS constant current source designed to provide precise constant current for driving LEDs from a varying input voltage source. It replaces discrete component solutions for driving LEDs in low-voltage applications such as 5V, 12V, or 24V systems, offering benefits in precision, integration, and reliability. The output current is set via an external sensing resistor connected to the FB pin, with a 100mV feedback voltage allowing low-value resistors to minimize power dissipation. A dedicated PWM input enables dimming control from a few Hz to 50kHz. An external capacitor on the SLOPE pin controls the current rise time, reducing EMI during switching transitions. The open-drain DISC pin provides diagnostic information on LED disconnection conditions.

The STCS2ASPR operates as a linear constant current regulator with four key subsystems: 1) Current Regulation Loop: The internal sense amplifier compares the voltage across the external feedback resistor (RFB) with the internal 100mV reference. The driver adjusts the main pass transistor to maintain 100mV across RFB, producing a constant LED current of ILED = 100mV / RFB. 2) PWM Dimming: When the PWM input is high, the main switch is on and current flows through the LEDs. When PWM is low, the switch turns off, enabling duty-cycle-based brightness control at frequencies up to 50kHz. 3) Slope Control: An external capacitor on the SLOPE pin controls the gate drive ramp rate, setting the current rise and fall times. This reduces EMI by limiting di/dt during switching. 4) Protection and Diagnostic: The thermal shutdown disables the output at 155C. The DISC pin monitors the drain voltage and indicates a load disconnection when the drain-to-ground voltage drops below 75mV.

• Low-voltage LED lighting systems powered from 5V, 12V, or 24V supplies
• Automotive interior and exterior LED lighting with PWM dimming
• Architectural and signage LED illumination
• RGB LED color mixing with independent current channels
• Industrial indicator and status LED arrays