CXLE8278 is a boost converter specially designed for LED Drivers. The input voltage range is 2.5V to 6V, and it supports up to 3 series of LED constant current drivers. The N-channel power MOSFETs with low on-resistance are integrated inside, and the current detection voltage is only 107mV, which greatly reduces the system loss and improves the overall efficiency. The chip adopts fixed 1MHz switching frequency, supports small inductance and ceramic capacitance, and is suitable for portable and embedded lighting equipment with compact space.
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[ CXLE8278 ]"
CXLE8278: high-efficiency boost LED driver chip helps the design of LED lighting system below 9W
In modern LED lighting systems, the efficiency, accuracy and reliability of the driving circuit directly affect the overall performance and service life. CXLE8278 as a boost DC/C LED driver integrated circuit based on CMOS technology, it integrates reference voltage source, oscillation circuit, error amplification circuit and current limiting circuit, it is suitable for efficient driving of 2-3 strings of LED, and the maximum output power can reach 9W. This article will comprehensively introduce the technical features, working principles and design points of CXLE8278, helping engineers build high-performance and high-reliability LED lighting solutions.
I. Product Overview
CXLE8278 is a boost converter specially designed for LED Drivers. The input voltage range is 2.5V to 6V, and it supports up to 3 series of LED constant current drivers. The N-channel power MOSFETs with low on-resistance are integrated inside, and the current detection voltage is only 107mV, which greatly reduces the system loss and improves the overall efficiency. The chip adopts fixed 1MHz switching frequency, supports small inductance and ceramic capacitance, and is suitable for portable and embedded lighting equipment with compact space.
Second, core features
• Wide input voltage range: 2.5V-6V, suitable for various power sources such as lithium battery and USB.
• High switching frequency: 1MHz, effectively reducing the inductance and capacitance volume.
• Low current detection voltage: 107mV (typical), significantly reducing the detection resistance loss.
• High-precision feedback benchmark: 1.25V ± 2% to ensure stable output voltage.
• Low quiescent current: the typical value is 60μa, and the light load efficiency is high.
• Built-in soft start: 2Ms start time, effectively suppress the impact current.
• Intelligent Protection mechanism: it has undervoltage locking (UVLO<2.3V) and adjustable current limiting function.
• Small size package: SOP8, good heat dissipation, suitable for high-density wiring.
• Simple peripheral circuit: only inductance, diode, capacitance and resistance are required to build a complete system.
Third, typical application scenarios
CXLE8278 is widely used in the following areas:
•2-3 String LED light bar, LED flashlight
•Portable lighting equipment, headlights
•Backlight drive system
•Car LED lighting
•All kinds of LEDs ≤ 9W lighting module
IV. Electrical characteristics and performance advantages
Under the typical conditions of VDD = 3.3V and ambient temperature 25℃, CXLE8278 shows the following superior performance:
•Feedback voltage accuracy: 1.25V ± 2%
•Maximum duty cycle: 78%
•Current limiting detection voltage: 107mV (typical)
•Shutdown current: ≤ 1nA
•Soft start time: 2ms
•Temperature stability: feedback voltage temperature drift ± 50ppm/℃
Its efficiency remains high under various input and output conditions. For example, when VIN = 3.6V, VOUT = 12V, and IOUT = 750mA, the efficiency can reach more than 92%, excellent energy conversion capability.
V. Functional description and Design Guide
5.1. Output voltage setting
The output voltage is set by the external divider resistance of the FB pin:
We recommend that RFB1 RFB2 be less than 200kΩ to reduce noise.
5.2. Output current setting
The output current is set through the external detection resistor of the VSENSE pin:
For example, when RSENSE = 143 Mohm, the output current is about 750mA.
5.3. Enable control
When the CE pin is high (>0.8V), the chip is enabled. When the CE pin is low (<0.4V), the power consumption is extremely low. If CE is not used, connect it to VDD.
5.4. Soft start and UVLO
The chip has built-in 2Ms soft start circuit to effectively suppress the Start impact. When VDD is less than 2.3V, the UVLO function automatically turns off the switching circuit to prevent misoperation.
5.5. Working mode description
CXLE8278 adopts peak current control architecture. When the built-in MOSFETs are turned on, the electric energy is stored in the inductor; When it is turned off, the inductor energy is released to the output through the diode to realize boost conversion. The system adjusts the duty cycle in real time through the feedback network to ensure the stability of the output voltage.
6. Peripheral components Model Selection Guide
6.1 inductance selection
3.3 μH power inductor is recommended to meet saturation current> peak inductor current. The peak current can be estimated as follows:
Where VD is the diode forward voltage drop (about 0.4V),fosc = 1MHz.
6.2 diode selection
The low voltage drop and fast recovery of the Schottky diode should be selected, and its reverse withstand voltage should be higher than VOUT, and the rated current should be greater than IPK.
6.3. Input and output capacitors
•Input capacitor (CIN): 10-22μf ceramic capacitor is recommended to suppress input ripple.
•Output capacitor (COUT): 22-44 LEDs F ceramic capacitor is recommended for smooth output voltage.
6.4. Divider resistance
RFB1 and RFB2 should choose high precision, good temperature characteristics of resistance, and as close as possible to the IC layout.
VII. Layout and heat dissipation suggestions
Good PCB design is crucial to improving efficiency and stability:
•The power path (VDD, LX, GND) should be short and wide to reduce parasitic parameters.
•FB and VSENSE are sensitive nodes and should be far away from switch signals such as LX.
•Chip GND should be directly connected to the system. Copper can be applied to the bottom of SOP8 package to enhance heat dissipation.
•Input and output capacitors should be close to the corresponding pin arrangement.
VIII. Packaging and supply information
CXLE8278 is packaged in SOP8, with compact size and good heat dissipation performance. It meets the green environmental protection standard and supports large-scale production and automatic mounting.
IX. Conclusion
With its high integration, low detection voltage, high switching frequency and perfect protection function, CXLE8278 has become an ideal driving scheme for LED lighting systems below 9W. No matter in portable lighting, vehicle-mounted lamps or industrial backlight applications, its excellent efficiency and reliability can meet the high requirements of modern electronic systems for power management. For detailed data manuals, sample applications, or further technical support, please visitJTM-IC official websiteQuery.
