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Automotive Electronics

AEC-Q100 Low-Side Constant Current Regulators for LED Driving

The TSCR420 & TSCR421 from Taiwan Semiconductor are low-side constant current regulators (CCR) for linear LED driving. These devices regulate with a preset 10mA nominal that can be adjusted with an external resistor up to 300mA. They are designed for driving LEDs in strings and will reduce current at increasing temperatures to self-protect.

Applications are expected to include ambient lighting, rear cluster lighting, interior lighting, puddle & sill lights, turn signals, reading lights, and so on.

Operating as a series linear CCR for LED string current control, these drivers can be used in multiple applications, as long as the maximum supply voltage to the device is <40V. With the low-side control, the TSCR421 has an Enable (EN) pin which can be pulse-width modulated (PWM) up to 10kHz by a microcontroller for LED dimming.

The output current at higher temperatures is controlled as a result of the negative temperature coefficient of 0.07%/°C of these LED drivers. Two or more TSCR420 & TSCR421 can be connected in parallel to construct higher current LED strings as shown below:

Application Circuit for Increasing LED Current

Summary of features:

  • AEC-Q100 qualified with the following results:
    • Device temperature grade 1: -40°C to 125°C
    • Device HBM ESD classification level H2
    • Device CDM ESD classification level C6
  • Low-side control Linear Constant Current Regulator:
  • LED drive current present 10mA
  • Very low enable current
  • Adjustable output current with external resistor up to 300mA
  • Supply voltage up to 40V
  • Easy paralleling of drivers to increase current
  • Good temperature coefficient vs. output current
  • Digital PWM input up to 10kHz (TSCR421CX6)
  • PPAP capable