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The BCR420U and BCR421U monolithically integrate transistors, diodes and resistors to function as a Constant Current Regulator (CCR) for linear LED driving. The device regulates with a preset 10mA nominal that can be adjusted with an external resistor up to 350mA. It is designed for driving LEDs in strings and will reduce current at increasing temperatures to self-protect. Operating as a series linear CCR for LED string current control, it can be used in multiple applications, as long as the maximum supply voltage to the device is < 40V.

With the low-side control, the BCR421U has an Enable (EN) pin which can be pulse-width modulated (PWM) up to 25kHz by a micro-controller for LED dimming.

With no need for additional external components, this CCR is fully integrated into a 2x2x0.6mm package (U-DFN2020-6) minimizing PCB area, off-board height, and component count.


  • Edge Lighting Strips
  • Emergency Lighting
  • Signage, Advertising, Decorative and Architectural Lighting
  • Retail Lighting in Fridges, Freezer Cases and Vending Machines


  • LED Constant Current Regulator Using NPN Emitter-Follower with Emitter Resistor to Current Limit
  • IOUT – 10mA ±10% Constant Current (Preset)
  • IOUT up to 350mA Adjustable with an External Resistor
  • VOUT – 40V Supply Voltage
  • PD up to 1.7W in U-DFN2020-6 Package
  • 0.6mm Height for Low-profile Edge Lighting
  • Low-Side Control Enabling PWM Input < 25kHz (BCR421U)
  • Negative Temperature Coefficient (NTC) Reduces IOUT with Increasing Temperature
  • Parallel Devices to Increase Regulated Current

Product Specifications

Product Parameters

Qualified to AECQ10x Yes
Automotive Compliant PPAP BCR421UFDQ
Topology Linear LED Driver
Minimum Supply Voltage 1.4 V
Maximum Supply Voltage 40 V
Maximum VOUT 40 V
Number of Channels 1
LED Current Sense Voltage 700 mV
Output Current 350 mA
LED Current 10 Preset mA
Accuracy 10 %
Dimming PWM
Temperature Range -55 to 150 °C

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Orderable Part Number Authorized Distributor Quantity Inventory Date Buy Online Region
BCR421UFD-7 Digi-Key Electronics 5773 6/24/2019 Buy Now Americas
BCR421UFDQ-7 Digi-Key Electronics 1064 6/24/2019 Buy Now Americas