Infineon BCR523U Low-Dropout Linear LED Driver: Datasheet, Application Circuit, and Design Guidelines
The Infineon BCR523U is a highly integrated, linear constant-current sink designed for driving LEDs with exceptional simplicity and reliability. As a member of Infineon's extensive LED driver portfolio, this device is engineered for low-voltage applications where space, efficiency, and stable performance are paramount. It eliminates the need for external components like series resistors, making it an ideal solution for compact and cost-sensitive designs.
Key Features from the Datasheet
The BCR523U is characterized by its very low dropout voltage, enabling efficient operation even when the input voltage is only marginally higher than the LED forward voltage. This is crucial for maximizing battery life in portable devices. The device regulates a fixed output current of 20 mA, with a tight tolerance of ±10%, ensuring uniform LED brightness. It offers excellent line and load regulation, maintaining a constant current despite variations in the supply voltage or forward voltage of the LED.
Housed in a miniature SOT-23-6 package, it features built-in protection against over-temperature conditions, which safeguards both the driver and the LED from damage. The datasheet also highlights a wide operating voltage range from 2.5 V to 40 V, providing significant flexibility for various applications, from automotive interior lighting to consumer electronics.
Typical Application Circuit
The application circuit for the BCR523U is remarkably straightforward, underscoring its ease of use. The basic configuration involves:
1. Connecting the anode of the LED string to the positive supply rail (VCC).
2. Connecting the cathode of the last LED directly to the OUT pin of the BCR523U.
3. Connecting the IN pin to the same VCC rail.
4. A single external resistor (REXT) connected to the REXT pin sets the output current. For the standard 20 mA, this resistor is typically 453 Ω.
5. The CTRL pin allows for dimming functionality. Applying a PWM signal to this pin enables brightness control by modulating the average current through the LED.
This minimalistic design requires no inductors or complex filtering, resulting in a very low-noise, EMI-compliant solution.
Essential Design Guidelines
To ensure optimal performance, several design considerations must be observed:
Thermal Management: As a linear regulator, power is dissipated as heat. The power dissipation is calculated as PD = (VIN - VLED) IOUT. It is critical to ensure that the junction temperature does not exceed the maximum rating of 150°C. Proper PCB layout with adequate copper pour for the device's pins is necessary to act as a heat sink.
Input Voltage Range: While the device can handle up to 40 V, the actual input voltage must be higher than the total forward voltage of the LED string (Vf_tot) plus the dropout voltage (VDO). For stable 20 mA output, ensure VIN > Vf_tot + VDO.
Dimming Implementation: For PWM dimming, a frequency between 100 Hz and 1 kHz is recommended to avoid visible flicker. The duty cycle of the PWM signal applied to the CTRL pin directly correlates to the LED's brightness level.
Parallel Operation: For driving multiple LED strings with matched current, multiple BCR523U devices can be used in parallel, each regulating its own 20 mA channel independently.
ICGOODFIND Summary
The Infineon BCR523U stands out as an exceptionally simple and robust solution for constant-current LED driving. Its low-dropout operation, integrated protection features, and minimal external component count make it a superior choice for space-constrained, battery-powered, and cost-optimized applications. Its ease of design and reliability solidify its position as a go-to component for designers seeking to implement high-quality LED lighting.
Keywords: Low-Dropout Regulator, Constant-Current Sink, LED Driver, PWM Dimming, Thermal Management.
