CXAC85214K is a non isolated buck constant current driver chip suitable for a wide input voltage range of AC176V~AC265V. It integrates high-precision current regulation module and line voltage regulation module internally, ensuring that the output current does not fluctuate with changes in inductance or LED operating voltage, and the output current accuracy is as high as ± 5%. The chip is equipped with a 500V high-performance power transistor and adopts advanced current detection technology. The system has extremely low power consumption and fewer peripheral components, effectively simplifying the design process, reducing system size and production costs.
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[ CXAC85214K ]"
CXAC85214K LED driver chip: high-precision non isolated constant current power supply solution
With the continuous development of LED lighting technology, the market demand for efficient, stable, and cost optimized driver chips is increasing. CXAC85214K, as a constant current power chip dedicated to LED lighting drivers, has become an ideal choice for various LED lighting applications due to its high integration, high-precision output, and comprehensive protection functions. This article will comprehensively introduce CXAC85214K from the aspects of chip characteristics, functional structure, electrical parameters, application design, and protection mechanism, to help engineers better understand and apply the chip.
1、 Chip Overview and Core Features
CXAC85214K is a non isolated buck constant current driver chip suitable for a wide input voltage range of AC176V~AC265V. It integrates high-precision current regulation module and line voltage regulation module internally, ensuring that the output current does not fluctuate with changes in inductance or LED operating voltage, and the output current accuracy is as high as± 5%. The chip is equipped with a 500V high-performance power transistor and advanced current detection technology. The system has extremely low power consumption and fewer peripheral components, effectively simplifying the design process, reducing system size and production costs.
This chip operates in the critical continuous mode of inductor current, without the need for auxiliary winding detection and power supply. It has ultra-low operating current and is suitable for various LED lighting products, such as LED light strips, bulb lights, etc.
2、 Functional characteristics and internal structure
The CXAC85214K integrates multiple practical functions and protection mechanisms:
• High precision constant current outputOutput current accuracy is controlled within± Within 5%, ensure consistent LED brightness.
• Built in 500V power transistorEnhance the system's voltage resistance and overall reliability.
• Multiple protection mechanismsIncluding LED open/short circuit protection, CS resistor short circuit protection, chip undervoltage protection, and overheat self adjustment function.
• Ultra low working currentOptimize energy efficiency, suitable for efficient and energy-saving lighting systems.
• SOP8 encapsulationCompact structure, easy to integrate and dissipate heat.
The internal structure of the chip includes key units such as power management module, current sampling comparator, demagnetization time control, driving logic, and power transistor, which work together to achieve precise constant current control and system protection.
3、 Pin function and electrical parameters
CXAC85214K adopts SOP8 packaging, and the functions of each pin are as follows:
• GND (pin 1)Chip grounding terminal.
• TP (Pin 2)Test pins, can be suspended or grounded.
• NC (Pin 3)Empty pin, it is recommended to connect to GND.
• VDD (pin 4)Chip power supply.
• DRAIN (pins 5 and 6)Built in high-voltage power transistor drain.
• CS (pins 7 and 8)Constant current sampling terminal, external sampling resistor set output current.
Under recommended operating conditions, the chip supports a maximum output current of 220mA, a peak current of 750mA for the power transistor, and a minimum LED load voltage greater than 15V. Its electrical characteristics include a VDD clamp voltage of 16.8V, a starting voltage of 13.8V, an undervoltage protection threshold of 9V, and a typical current detection threshold of 400mV.
4、 Typical Applications and Design Points
4.1. System startup and workflow
After the system is powered on, the bus voltage charges the VDD capacitor through the starting resistor. When the VDD voltage reaches 13.8V, the chip starts up and begins to operate. VDD is clamped by an internal 17V voltage regulator and does not require auxiliary winding power supply.
4.2. Output current setting
The output current is set through an external sampling resistor (R_CS) connected to the CS pin. The formula for calculating the peak current of an inductor is:
The average output current of LED is half of the peak current:
4.3. Inductance selection and system frequency
The system operates in critical conduction mode, and the inductance calculation formula is as follows:
Among them, the system frequency f varies with the input voltage. The chip has set a minimum demagnetization time of 2µ S and maximum demagnetization time of 240 μ m; s. Choosing the appropriate inductance value is crucial as both too small and too large inductance can cause the system to enter intermittent or continuous mode, affecting output accuracy.
4.4. PCB design suggestions
• The VDD bypass capacitor should be closely attached to the chip pins.
• The DRAIN pin needs to increase the copper foil area to enhance heat dissipation.
• The area of power loops (inductors, power tubes, bus capacitors, etc.) should be minimized as much as possible to reduce EMI radiation.
• The sampling resistor ground wire should be short and thick, and routed separately from the signal ground, ultimately converging at the bus capacitor ground terminal.
5、 Comprehensive protection mechanism
CXAC85214K has comprehensive protection functions to ensure the safety and reliability of the system in various abnormal situations:
• LED open/short circuit protectionThe system stops working when there is an open circuit; During a short circuit, the system operates at a low frequency of 5kHz, reducing the CS threshold to 200mV and lowering power consumption.
• CS resistor short circuit protectionQuickly detect and shut down the system to prevent component damage.
• Undervoltage protectionWhen VDD is below 9V, the system enters the undervoltage protection state.
• Overheating regulationWhen the junction temperature exceeds 150 ℃, the chip automatically reduces the output current and controls the temperature rise.
The system will periodically detect the load status in a protected state, and if the fault is resolved, it will automatically resume normal operation.
6、 Conclusion
The CXAC85214K provides an efficient and reliable constant current drive solution for LED lighting systems with its high precision, high integration, and comprehensive protection functions. Its simple peripheral circuit and flexible configuration options greatly reduce the design threshold and production cost, making it suitable for various civilian and commercial lighting scenarios.
For more technical information, sample requests, or procurement information about CXAC85214K, please visit our official website:jtm-ic.comWe are committed to providing customers with high-quality integrated circuit solutions and professional technical support services.
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