CXLE8275XS is a highly integrated LED driver controller, packaged in BPSOP10, suitable for non isolated buck LED driver solutions. Its biggest highlight is its support for adjusting the output current through an external dip switch, with a range of up to 40% to 100%. During this process, the overvoltage protection (OVP) voltage is not affected by the current level, greatly improving the reliability and safety of the system.
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[ CXLE8275XS ]"
CXLE8275XS: A high-performance DIP dimming non isolated LED constant current driver chip
In today's LED lighting systems, efficient, stable, and flexible driving solutions are key to achieving a high-quality lighting experience. CXLE8275XS, as a non isolated step-down LED constant current driver chip designed specifically for dip switch dimming, has become an ideal choice for high-power LED lighting design due to its excellent performance, high integration, and flexible configurability. This article will delve into the core features, working principles, application design guidelines, and advantages of CXLE8275XS in lighting systems.
1、 Chip Overview and Core Features
CXLE8275XS is a highly integrated LED driver controller, packaged in BPSOP10, suitable for non isolated buck LED driver solutions. Its biggest highlight is its support for adjusting the output current through an external dip switch, with a range of up to 40% to 100%. During this process, the overvoltage protection (OVP) voltage is not affected by the current level, greatly improving the reliability and safety of the system.
The chip integrates 500V high-voltage power MOS transistors and high-voltage JFET power supply lines internally, without the need for external VCC capacitors and starting resistors, significantly simplifying peripheral circuits, reducing system costs and PCB area. In addition, the CXLE8275XS offers four selectable fixed OVP voltages (135V, 225V, 320V, and unlimited), which users can flexibly configure through a single external resistor to meet different output voltage requirements.
2、 Detailed explanation of main functions
2.1. DIP switch dimming and DIM control
The DIM pin of CXLE8275XS is the core of its dimming control. The pin is integrated with a 20μ A pull-up current source, and different ground resistors can be switched through an external dip switch to change the voltage of the DIM pin, thereby linearly adjusting the internal reference voltage of the CS comparator, achieving stepless or gear adjustment of the LED output current. In addition, the DIM pin also has an enable function. When the voltage drops below 100mV, the chip stops working and can be used for mechanical switch color adjustment, induction control, or remote power on/off. If capacitors are connected in parallel at the DIM pin, soft start function can also be achieved to reduce startup shock, especially suitable for circuits with PFC in the front-end to reduce component stress.
2. Intelligent Overvoltage Protection (OVP)
Open circuit protection is an important safety mechanism in LED drivers. The CXLE8275XS sets four OVP thresholds through an external resistor on the ROVP pin to ensure timely protection in case of LED open circuit or abnormal high voltage. Once triggered, the chip enters“ Hiccup” Mode, periodically restart until the fault is resolved. This design not only protects the system but also has self recovery capabilities.
2.3. Critical conduction mode and efficient constant current control
The chip operates in critical continuous mode (BCM) of inductor current, without the need for auxiliary winding detection demagnetization, further simplifying transformer design. It precisely controls the peak current of the inductor by detecting the current sampling voltage on the CS pin cycle by cycle, comparing it with the internal adjustable threshold, and achieving high-precision constant current output. Its LED current accuracy can reach± 5%, with excellent line voltage regulation and load regulation.
2.4. Comprehensive protection mechanism
The CXLE8275XS is equipped with multiple protection functions, including:
· LED short circuit protectionWhen a short circuit occurs, the system automatically drops to low frequency operation with extremely low power consumption.
· Chip undervoltage protectionEnsure reliable shutdown in case of insufficient power supply.
· Cycle by cycle current limitingPrevent overcurrent damage.
· Overheating regulationWhen the junction temperature exceeds 150 ℃, the output current is automatically reduced to control the temperature rise and improve the long-term reliability of the system.
3、 Design Guidelines and PCB Layout Suggestions
3.1. Power inductance calculation
The selection of inductance value is crucial in critical conduction mode. The calculation formula is as follows:
Among them, VLED is the LED string voltage, VIN is the input DC voltage, IPK is the peak current of the inductor, and f is the operating frequency. It should be ensured that the system frequency is not lower than the design minimum value at the lowest input voltage; At the highest input voltage, the demagnetization time should not exceed the maximum turn off time of the chip (typically 450 μ s) to avoid entering continuous or deep intermittent mode that affects current accuracy.
3.2. Key points of PCB layout
Good layout is crucial for performance and EMI:
3.2.1 Current sampling pathThe grounding path of the CS resistor should be as short and thick as possible, and independently led to the input capacitor grounding point to avoid power noise interference.
3.2.2 High voltage isolationThe HV pin should be kept away from low-voltage signal pins such as CS and DIM.
3.2.3 Minimize power loopReduce the loop area formed by power inductors, MOSFETs, input capacitors, as well as the loop area of inductors, freewheeling diodes, and output capacitors to reduce electromagnetic radiation.
3.2.4 Heat dissipation treatmentFully utilize the GND pin and surrounding copper foil for heat dissipation, especially for high current applications.
4、 Typical application scenarios
The CXLE8275XS is highly suitable for various medium to high-power LED lighting products, including:
· Mining lights, high ceiling lights
· Street lights, tunnel lights
· Commercial spotlights, floodlights
Other constant current drive scenarios that require dimming or adjustable current
Its dial-up dimming feature is particularly suitable for scenarios that require on-site installation and debugging or segmented dimming, while the flexible OVP setting can adapt to different LED string voltage schemes.
5、 Limit parameter
Note 1: The maximum limit value refers to the possibility of chip damage if it exceeds the working range. The recommended working range refers to the range within which the device functions normally, but it does not fully guarantee the fulfillment of individual performance indicators. Electricity parameter setting
Specify the DC and AC parameters of the device within its operating range and under testing conditions that ensure specific performance indicators. For parameters without given upper and lower limits, this specification does not guarantee their accuracy, but their typical values
Reasonably reflects the performance of the device.
Note 2: As the temperature increases, the maximum power consumption will inevitably decrease, which is also due to TJMAX,θ JA, And the ambient temperature T Decided upon. The maximum allowable power consumption is PA
DMAX = (TJMAX - TA)/ θ JA or the lower value given by the limit range.
Note 3:1 square inch double-layer PCB board, tested according to JEDEC standards.
Note 4: According to JEDEC standards, a 100pF capacitor passes the 1.5K&Omega test; Resistance discharge.
6、 Electrical parameters (Note 5) (Unless otherwise specified, TA=25 ℃)
7、 Internal structure diagram
8、 Packaging and Pin Function
9、 Typical schematic diagram
10、 Conclusion
The CXLE8275XS provides an excellent solution for LED driver design due to its high integration, reliability, and flexibility. Whether it is simplifying the periphery, reducing costs, or achieving safe and reliable dimming and control, this chip performs excellently. For more detailed technical information, application notes, or procurement information, please visit our official website;jtm-ic.comLearn more about CXLE8275XS and its full range of LED driver chips.
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