Although Switch-mode and PWM or Pulse Width Modulation methods make very efficient drivers for LEDs, they are also a good source of electromagnetic noise. Many applications require low noise conditions for proper operations, especially those related to medical. These low-noise applications benefit from linear circuits that introduce far lower noise in the system as compared to the Switch-mode or PWM topologies.

For driving LEDs linearly, Infineon Technologies AG offers a small LED driver IC, the BCR431U. Available in a tiny SMT package SOT23-6, the BCR431U can regulate the operating current to the LED in a standalone operation without requiring the help of an external power transistor.

Operating between a voltage range of 6 to 42 VDC, the BCR431U can drive LED currents up to 37 mA. A high-value resistor connected between the pins Rset and RS of the IC allows setting the desired LED current level.

The major advantage of the BCR431U LED driver is its low-drop feature. At a full load of 37 mA, the IC drops only 200 mVDC across from the supply to the output. At 15 mA load, this voltage drop is only 105 mVDC. This feature has two benefits—one, the power dissipation in the driver IC at full load is only 7.4 mW, and two, the user can drive a string of LEDs in series connection mode by adjusting the input voltage. Over the entire current range, the driver IC maintains precision of ±10% of the set value of the LED current.

The low voltage drop across the BCR431U LED driver improves the system efficiency substantially while allowing extra voltage headroom to compensate for the tolerances of forward voltages of LEDs. Therefore, even if some LEDs in the string have different forward voltages, the driver IC can accommodate them with an increase or decrease in the driving voltage. Likewise, it can accommodate tolerances in supply voltage sources when used in multiple applications.

Internal circuit configurations ensure the BCR431U LED driver IC can keep the LED current under control, even when the temperature changes. If the junction temperature of the driver IC rises, a temperature controlling circuit within the IC reduces the LED current, thereby helping to bring down the junction temperature. Therefore, the BCR431U can protect itself from thermal runaway.

The linear low-drop LED current driver IC BCR431U is eminently suitable for driving long strips of low-power and low-voltage LEDs. Highly flexible in adjusting to 12, 24, or 36 VDC power supplies, the driver IC offers high precision and efficiency when driving LEDs. Internal thermal protection built into the driver IC ensures long-life operations, preventing accidental damages and protections against surge events. Infineon has designed the IC BCR431U to be robust enough to withstand high ESD conditions.

Applications for BCR431U are almost endless including driving LED strips, LED channel letters and displays, architectural LED lights and displays, emergency lights, retail lights for decoration, shop window LED lights, and many more. The driver IC is especially helpful in shops for driving LED lights in shops showcasing items in different colors.