Diodes Incorporated BCR421UFD-7

Overview

BCR421UFD-7 from Diodes Incorporated is a monolithic linear LED constant current regulator (CCR) in U-DFN2020-6 package, functioning as a low-side PWM-controllable current sink with 10mA nominal preset output, adjustable up to 350mA via external resistor R_EXT, 40V max supply voltage, and -0.2%/°C negative temperature coefficient for self-protection - used in edge lighting strips and retail freezer case illumination.

For engineers reviewing the BCR421UFD-7 datasheet, BCR421UFD-7 pinout, BCR421UFD-7 application, or BCR421UFD-7 equivalent, this device supports 25kHz PWM dimming, delivers stable current under varying V_OUT (1.4–40V), integrates internal 95Ω bias resistor, requires no inductors or capacitors, and operates across -55°C to +150°C junction temperature range.

Technical Context

The BCR421UFD-7 implements an NPN emitter-follower topology with integrated emitter resistor (R_INT = 95Ω typ) and enable-controlled bias transistor, delivering precise current regulation independent of LED forward voltage variation. Its low-side control architecture places the regulated current path between OUT and GND, enabling direct microcontroller PWM drive on the EN pin.

Thermal protection is achieved via inherent negative temperature coefficient: output current decreases by 0.2%/°C above 25°C, reducing power dissipation during thermal stress. Power handling is defined by R_θJA = 75°C/W (50mm×50mm copper) and maximum 1.7W dissipation, requiring PCB copper area optimization per thermal derating curves.

Key Specifications

Pinout & Package

U-DFN2020-6 package: 2.0mm × 2.0mm body, 0.6mm height, NiPdAu-plated terminals, moisture sensitivity level 1, UL 94V-0 molding compound.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar LED constant current regulation applications.

Compared with BCR420UFD-7, the BCR421UFD-7 adds PWM dimming at no cost penalty in footprint or thermal performance; versus AL5809-20EVB, it trades efficiency for simplicity, size, and EMI immunity - ideal for <200mA, space-constrained, noise-sensitive lighting.

Availability

BCR421UFD-7 is available at Aetrix Electronics and suitable for edge lighting strips, retail freezer case lighting, and emergency exit signage requiring stable component supply, long-term lifecycle assurance, and RoHS 3-compliant manufacturing.

Supply support for BCR421UFD-7 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Diodes Incorporated is a global semiconductor company specializing in discrete, analog, and mixed-signal ICs, with design centers in Asia, Europe, and the US, and manufacturing in ASE, Amkor, and its own facilities.

The BCR421UFD-7 belongs to Diodes' Linear LED Driver product line, engineered specifically for cost-sensitive, space-constrained, and thermally challenging LED lighting applications where simplicity, reliability, and regulatory compliance are prioritized over switching efficiency.

FAQ

What is the minimum voltage required across BCR421UFD-7 to maintain regulation?

The device requires a minimum output voltage (V_OUT(MIN)) of 1.4V at I_OUT > 18mA to sustain regulation. Below this, current drops nonlinearly. This headroom accommodates typical LED forward voltages while ensuring stable operation across temperature and process variation.

Can BCR421UFD-7 drive multiple parallel LED strings?

Yes - multiple BCR421UFD-7 devices can be paralleled by connecting all OUT and EN pins together, provided identical R_EXT values and matched PCB copper layout. This scales total current capacity while preserving per-string regulation accuracy and thermal balance.

How does the -0.2%/°C temperature coefficient affect LED brightness stability?

The coefficient causes I_OUT to decrease linearly with rising junction temperature, reducing LED power and heat generation. In steady-state operation, this results in ~15% lower current at 100°C vs. 25°C - a deliberate trade-off to prevent thermal runaway in enclosed fixtures without active cooling.

Is the EN pin compatible with 5V microcontrollers?

No - the absolute maximum EN voltage is 18V, but the recommended operating EN voltage is 3.3V (typical test condition). Driving with 5V logic risks exceeding the 1.2mA enable current specification and may degrade long-term reliability; a 3.3V-compatible MCU or level shifter is required.