Taiwan Semiconductor augmented its existing TSCR4xx line of LED drivers with two new low-side constant current regulators for automotive LEDs.

TSC recently announced the availability of the TSCR420CX6H and the TSCR421CX6H. The AEC-Q100 qualified LED drivers regulate with a preset 10mA nominal current that can be adjusted up to 300 mA via an external resistor. They are designed for driving LEDs in strings and will self-protect by reducing current at increasing temperatures, with a negative temperature coefficient of 0.07%/°C.


Taiwan Semiconductor’s LED Driver. Image source: Taiwan Semiconductor


The devices operate as series linear constant current regulators (CCR) for LED string current control. The TSCR421CX6H has a maximum input voltage of 4.5V, while its sister product, the TSCR420CX6H and it can be used with a maximum input voltage of < 40V. Both devices can work with supply voltages up to 40V.


Typical Applications

These new automotive LED drivers will find broad applications including:

  • Ambient light
  • Interior light
  • Turn signals
  • Rear cluster lighting
  • Puddle & Sill lights
  • Reading light
  • Instrument cluster illumination

Both devices are low side regulators, meaning that they attach electrically to ground, rather than to the VS Supply. The TSCR421CX6H can be pulse-width modulated (PWM) up to 10 kHz by a microcontroller for LED dimming.

Circuit diagrams for the TSCR420CX6H (l) and the TSCR421CX6H (r). Images courtesy Taiwan Semiconductor.


If more than 300 mA needs to be sourced, these automotive LED drivers can be hooked up in parallel.


Industry Standards

The devices are 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

TSC’s line of linear LED drivers lists many more features, including devices with maximum input voltages of 4.5, 40, and 50 volts.



Taiwan Semiconductor is an exceptionally large semiconductor foundry, and while these drivers offer unique elements, the competition displays a strong similarity in the parts numbers and specs.


 • BCR42OU and BCR32OU for the TSCR420CX6H

The main difference between the two is that the BCR320U has a maximum supply voltage of 25V, and the BCR420U has a maximum supply voltage of 40V.

 • BCR421U and BCR321U for the TSCR421CX6H

Digital PWM input frequency up to 10 kHz for dimming. Again, the main difference between the two is that the BCR321U has a maximum supply voltage of 25V, and the BCR421U has a maximum supply voltage of 40V.

Diodes Incorporated

 • BCR420UW6Q for the TSCR420CX6H

VOUT up to –40V supply voltage.

 • BCR421UW6Q for the TSCR421CX6H

Also VOUT up to –40V supply voltage. This device can be pulse-with modulated, like the TSCR421CX6H, with input frequency of up to 25 kHz for dimming.