The CXLE8275XD adopts advanced full cycle closed-loop inductor current sampling technology, which achieves excellent constant current accuracy and load adjustment rate through real-time control of the average inductor current. Even under a wide range of output voltages, the chip can maintain stable current output, ensuring uniform and consistent LED brightness.
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[ CXLE8275XD ]"
CXLE8275XD: Efficient and Stable LED Constant Current Driver Chip Solution
In today's increasingly popular LED lighting applications, the performance of driver chips directly affects the stability, energy efficiency, and lifespan of lighting fixtures. Jiatai Mu（jtm-ic.com）LaunchedCXLE8275XD, is an LED constant current driver chip designed specifically for low power factor (PF) floating Buck architecture. With its high precision, reliability, and integration, it has become an ideal choice for industrial and commercial lighting such as LED three proof lights and line lights.
1、 Chip Overview and Core Advantages
CXLE8275XD adopts advanced technologyFull cycle closed-loop inductor current sampling technologyBy real-time control of the average inductance current, excellent constant current accuracy and load adjustment rate have been achieved. Even under a wide range of output voltages, the chip can maintain stable current output, ensuring uniform and consistent LED brightness.
This chip integrates500V High Voltage MOSFETSimplified peripheral circuit design, reduced system cost and volume. Its uniqueDigital current regulation functionBy connecting the CS pin resistor externally, the output current can be flexibly set, avoiding the risk of traditional dip switches carrying high currents and improving system reliability and service life.
2、 Detailed explanation of key characteristics
2.1 High precision constant current control
The chip integrates a high-precision voltage reference (3%) internally, combined with a full cycle sampling mechanism, to ensure accurate and stable output current, meeting the stringent requirements of high-end lighting applications for light quality.
2.2 Comprehensive protection function
CXLE8275XD has built-in multiple protection mechanisms, including:
In addition, the chip supportsExternal NTC resistorThe implementation of temperature adjustable over temperature current reduction function effectively prevents the lamp from being damaged due to overheating, greatly improving the reliability of the system in high temperature environments.
· VCC undervoltage lockout (UVLO)
· Cycle by cycle current limiting protection (OCP)
· Output Open Circuit Protection (OVP)
· Output short circuit protection (SCP)
· Built in over temperature drop current protection (OTP)
2.3 Excellent EMC performance
The chip adopts critical conduction and frequency limiting working modes, optimizing electromagnetic compatibility design, which helps the system easily pass various EMC tests, reduce peripheral filtering components, and lower overall costs.
2.4 Wide voltage operating range
Supports ultra wide output voltage loads, adapts to various LED series and parallel configurations, and has strong design flexibility.
3、 Typical application areas
· LED three proof light (dustproof, waterproof, anti-corrosion)Suitable for harsh environments such as warehouses, parking lots, tunnels, etc.
· LED strip lightUsed for commercial lighting, decorative lighting, advertising lightboxes, and other scenarios that require high consistency and long lifespan.
4、 Design Guidelines and PCB Layout Suggestions
To ensure optimal performance of CXLE8275XD, the following points should be noted when PCB layout:
· Power decouplingThe capacitor next to the VCC pin should be as close to the chip as possible to reduce noise interference.
· Current sampling pathThe power ground of the current sampling resistor should be thick and short, and close to the GND pin of the chip to ensure sampling accuracy.
· Reduce the area of the loopThe layout of power circuits (such as input capacitors, MOSFETs, inductors, and output capacitors) should be compact to reduce EMI radiation.
· FB pin wiringThe FB voltage divider resistor should be close to the FB pin and away from noise sources (such as transformers). It is recommended to add a small capacitor filter between FB and GND.
· NTC filteringConnecting capacitors in parallel between the NTC pin and GND can suppress the impact of switch noise on temperature detection.
When designing the CXLE8275XD PCB board, the following points should be noted:
1) The bypass capacitor of VCC needs to be closely connected to the VCC and GND pins of the chip.
2) The power ground wire of the current sampling resistor should be as thick as possible and as close as possible to the ground of the chip to ensure the accuracy of current sampling. The dip resistor should be placed close to the chip. In addition, the signal ground needs to be separately connected to the ground pin of the chip.
3) Reduce the surface area of high current loops, such as the surface area of line capacitors, power transistors, power inductors, and output capacitors, as well as the surface area of power inductors, freewheeling diodes, and output capacitors, to reduce EMI radiation.
4) The voltage divider resistor connected to FB must be close to the FB pin and the node must be far away from the moving point of the transformer, otherwise system noise can easily trigger the FB OVP protection function. Suggest placing a filtering capacitor between FB and chip GND to avoid system noise interference.
5) Place a filtering capacitor between the NTC pin and the chip GND to avoid the influence of system switching noise
5、 Typical applications
CXLE8275XD is an LED constant current driver chip specifically designed for low PF floating Buck. It adopts full cycle closed-loop sampling to improve constant current accuracy. CXLE8275XD
The CS pin supports setting the output current by selecting different resistors through a dip switch, which can avoid large currents flowing through the dip switch, prolong the service life, and also avoid
The power circuit cable passes through.
3. Start up
After the system is powered on, the input voltage is applied through the starting resistor; VCC Capacitor charging, when VCC When the voltage reaches the chip's turn-on threshold, the internal control circuit of the chip starts working,
COMP voltage is quickly established. Then CXLE8275XD starts outputting pulse signals, and when the FB voltage is below 0.2V, the system operates in TOFFmax state. When FB is introduced
After detecting a positive voltage level greater than 0.25V, CXLE8275XD switches to closed-loop operation.
4. Constant current control and output current setting
The CXLE8275XD adopts an inductor current full cycle current sampling mechanism, which can achieve high-precision output constant current control over a wide range of load voltages. Calculation method for LED output current:
VREF is the internal reference voltage
RCS is the value of the current sampling resistor
5. FB feedback control
CXLE8275XD detects the zero crossing state of the inductor current through the FB pin, with the rising threshold voltage set to VFB_RiSE and the falling threshold voltage set to VFB_FALL for FB. FB Introduction
The foot can also be used to detect the output voltage for output overvoltage protection. When the FB voltage triggers the overvoltage protection threshold VFB_OVP, the chip enters protection. The ratio of the upper and lower voltage divider resistors of FB can be calculated according to the following formula:
It is the set value VOVP for output voltage overvoltage protection
RFBH is the upper voltage divider resistor of the feedback network
RFBL is the voltage divider resistor of the feedback network
among which
The CXLE8275XD has an overheat regulation function, which gradually reduces the output current when the drive power supply overheats, thereby controlling the output power and temperature rise to maintain the temperature of the drive power supply
Set values to improve system reliability. The chip is internally set to TREG as the temperature point for overheat regulation.
7. External NTC over temperature current reduction function
CXLE8275XD supports external NTC and achieves adjustable over temperature point. When the NTC voltage is VNTC or above, the over temperature regulation is TREG, and when the NTC voltage starts to be less than
When VNTC, the external NTC over temperature and current drop function starts working. The relationship between the NTC pin and the internal constant current reference is shown in the following figure. When the NTC voltage is lower than VNTC_LALL,
The system stops the switch action. When the NTC voltage returns to VNTC-IN or above, the system resumes operation.
The CXLE8275XD is equipped with multiple protection functions to ensure system reliability.
FB detection enhances anti-interference and system reliability. When the LED is open circuited, the output voltage gradually increases, and the voltage detected by FB also increases accordingly. When the voltage detected by FB rises to the VFB_OVP threshold, the protection logic will be triggered and the switch will stop working. VCC will be discharged by the chip to below the UVLO voltage and enter the fault protection state.
When the LED is short circuited, FB cannot detect demagnetization signal, and the system operates in TOFFmax state. At the same time, the internal overcurrent protection voltage threshold is reduced to VCS-TH2, thereby reducing system power consumption.
When the output is short circuited or the transformer saturates, the peak voltage of CS will be relatively high. When the CS voltage rises to the internal limit value, the switch cycle stops. This cycle by cycle current limiting function can protect power MOSFETs, transformers, and output freewheeling diodes.
7、 Limit parameters (Note 1)
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.
8、 Electrical parameters (Note 4) (Unless otherwise specified, T =25℃）
9、 Conclusion
CXLE8275XD provides strong core support for LED driver solutions with its high integration, reliability, and flexible design features. Whether facing harsh industrial environments or pursuing high-quality commercial lighting, this chip can provide stable, efficient, and safe driving solutions.
For more technical information, application notes, and procurement information about CXLE8275XD, please visitjtm-ic.comShanghai Jingtong Microelectronics is committed to providing customers with comprehensive technical support and high-quality semiconductor product services.
