Taiwan Semiconductor Unveils Drop-in Replacements for Legacy Bipolar Drivers

The new constant-current CMOS LED driver ICs enable upgrades of existing designs for higher performance while requiring no redesign effort.

The TSCR4 family of linear LED driver ICs provides the stable current essential to the optimal operation of modern LED lighting systems. Members of the new family of high-side constant current regulators (CCRs) include the TSCR400 and the TSCR402 which are preset to regulate at 0.1 mA and 20 mA, respectively. Operation at up to 65 mA can be effected with the application of an external resistor.

The new devices offer enhanced stability over a range of real-world conditions, including changing load demands, and variations in source voltage or changes in temperature. The TSCR4 family affords both greater current setpoint stability and tighter output compliance voltage when compared to previous solutions.

 

Image courtesy of Taiwan Semiconductor (TSC)

 

Key Attributes of the TSCR400 and the TSCR402 

• Maximum supply voltage for both devices is 40 volts
• The devices can be used in parallel if higher drive current is called for
• Quiescent current at 24 volts is 300 mA.
• PWM dimming from 0 to 100% is possible
• Output current decreases by -0.07%/°C of the device to prevent thermal runaway
• Output voltage drop is typically as low as 0.65 volts

 

Applying the TSCR400 and the TSCR402 

According to Taiwan Semiconductors (TSC), these units enable effortless improvement of existing designs because they can serve as direct drop-in replacements 

As noted by Sam Wang, Taiwan Semiconductor’s (TSC) Vice president, “The TSCR4 family of LED driver ICs is the perfect part to upgrade a legacy design”. He goes on to state that “The features and performance of these devices at an affordable price point make them an excellent candidate for new designs, as well.” 

Because there is no need for external components such as switching diodes,  inductors or capacitors, use of these new LED drivers enables designers to save considerable PCB real estate, especially when compared to more complex solutions based on switching regulators.

As illustrated in the diagram below, both devices include the internal resistor, RINT, valued at 6.5 kΩ and 44Ω for the TSCR400 and TSCR402, respectively. 

 

Typical application circuit for the TSCR400 and the TSCR402. Image used courtesy of TSC Datasheet

 

It is through choosing an appropriate value for REXT that the units can be caused to source as much as 65 mA.

 

Applications for the TSCR4 family

• Decorative lighting
• Exterior and interior lighting for motor vehicles
• Electronic signage
• Architectural lighting
• Lighting for appliances and kiosks
• Emergency lighting

 

Physical Characteristics

Members of the new family are halogen-Free according to IEC 61249-2-21. They are also lead free and are compliant to RoHS Directive 2011/65/EU and in accordance to WEEE 2002/96/EC. They are available in SOT-26 packages and operate over a junction temperature range of 55 to 150 ℃. If needed, AEC-Q100 rated versions of the units are available.