CXLE82128 is a current-mode boost converter dedicated to driving white LEDs in series. The input voltage range is 2.3V to 6V, which can be directly powered from a single lithium ion battery or USB power supply. The output can drive up to 8 Series LEDs, and the output voltage can reach up to 27v. MOSFETs with low on-resistance (50mΩ) are integrated inside the chip, with excellent conversion efficiency. The typical switching frequency is 800kHz, which is helpful to reduce the size of peripheral components.
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[ CXLE82128 ]"
CXLE82128: efficient and flexible white LED driver chip solution
In modern portable electronic devices, white LED is widely used in backlight and lighting systems due to its high brightness, low power consumption and long service life. To meet diverse driving requirements, CXLE82128 is a high-performance boost DC/DC converter designed for driving multiple strings of white LED, with programmable current, wide input voltage range, it integrates advanced functions such as overvoltage protection and PWM dimming. This article will comprehensively analyze the technical characteristics, application design points and advantages of CXLE82128 in various electronic products.
I. CXLE82128 overview of core features
CXLE82128 is a current-mode boost converter dedicated to driving white LEDs in series. The input voltage range is 2.3V to 6V, which can be directly powered from a single lithium ion battery or USB power supply. The output can drive up to 8 Series LEDs, and the output voltage can reach up to 27v. MOSFETs with low on-resistance (50mΩ) are integrated inside the chip, with excellent conversion efficiency. The typical switching frequency is 800kHz, which is helpful to reduce the size of peripheral components.
The chip has the following outstanding features:
· Programmable LED current: The LED current is precisely set by external resistor (RSET), and the formula is LED = 200mV/RSET.
· Wide range PWM dimming: supports dimming frequency from 20kHz to 360kHz, which can realize smooth brightness adjustment without flicker.
· Programmable overvoltage protection (OVP): set the OVP threshold through an external resistor to prevent the output voltage from being too high when the LED is open or abnormal.
· Low quiescent current: The typical static current is only 100 μA, and the shutdown current is as low as 20 μA, which is beneficial to prolong the battery life.
· Miniature package: it adopts SOP8/PP package with heat dissipation pad, which is suitable for portable devices with compact space.
II. Detailed explanation of key functions
2.1. Accurate LED current control
CXLE82128 detects the voltage drop (typical 200mV) on the external resistor RSET through the FB pin to adjust the LED current in real time to ensure that the current does not fluctuate with the input voltage or the number of LEDs. We recommend that you use a resistor with an accuracy of 1% to achieve a more stable current output.
2.2. Flexible PWM dimming scheme
The chip supports injecting PWM signals through FB pins for dimming. During the PWM high level, the LED operates at full current; During the low level, it is completely closed. The average brightness is proportional to the PWM duty cycle, and the dimming frequency range is wide (20kHz-360kHz) to avoid audible noise, which is suitable for applications with high display quality requirements.
2.3. Integrated overvoltage protection mechanism
When the LED is open or the load is abnormal, the output voltage may rise to a dangerous level. CXLE82128 built-in OVP circuit, you can set the protection threshold through the external divider resistance. Once the output voltage exceeds the set value, the chip immediately turns off switch tube until the voltage falls back to the safe range, effectively protecting the chip and LED.
3. Typical application scenarios
CXLE82128 is suitable for a variety of portable devices that require efficient LED drivers, including:
·Backlight drivers for smartphones, tablets and PDAs
·MP3 player. Audio devices such as Bluetooth headphones
·GPS navigator and handheld terminal
·Portable medical equipment and industrial instrument display
It has high integration and small package characteristics, especially suitable for applications with limited space and sensitive to power consumption.
IV. Design guide and selection suggestions
4.1. Inductance selection
We recommend that you use ferrite magnetic core inductor to reduce high frequency loss. The inductance value needs to be calculated according to the input and output voltage, LED current and switching frequency. Generally, it is recommended to use the inductance in the range of 10 kHz to 22 kHz.
4.2 diode selection
In order to improve efficiency, fast recovery Schottky diode should be selected, and its reverse withstand voltage should be higher than the maximum output voltage.
4.3. Input and output capacitors
Input capacitor (CIN) is used to suppress power supply noise. It is recommended to use ceramic capacitor with low ESR, and the capacitance value is usually 10μf. Output capacitor (COUT) also recommends low ESR Capacitor to reduce output voltage ripple and improve system stability.
4.4 layout and heat dissipation suggestions
The SW pin is a high-frequency switch node, which should be kept short and thick and away from sensitive signals. The heat dissipation pad at the bottom of the chip must be copper foil welded with the PCB to enhance the heat dissipation performance. It is recommended to arrange filter capacitor near the VIN pin and place it as close to the chip as possible.
V. Packaging and pin functions
6. Typical schematic diagram
VII. Why did you choose CXLE82128?
CXLE82128 is an ideal choice for driving multiple strings of white LED due to its high efficiency, high integration and rich protection functions. Its programmable characteristics make the design flexible and changeable, and it can be easily realized whether it is constant current drive or dimming control. Combined with small package and low power consumption, the chip can significantly improve the performance and reliability of terminal products.
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