CXLB73279 is a synchronous step-down lithium ion battery charging management chip that supports 4.6V to 26V wide voltage input. It adopts a fixed 550kHz switching frequency and has a charging efficiency of more than 90%, greatly reducing the heating of the chip itself. Its internal integration of 28V high-voltage devices, can effectively resist the surge voltage or the risk of misconnection of high-voltage adapter, with high system security.
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[ CXLB73279 ]"
High efficiency 2.5A Li-ion battery charger CXLB73279: wide voltage input and multiple intelligent protection
With the popularity of portable electronic devices, there is an increasing demand for efficient, safe, small-sized battery charge management chips. As a 2.5A high-efficiency charger chip designed for lithium-ion batteries, CXLB73279 not only has a wide voltage input range and high efficiency characteristics, but also integrates multiple protection mechanisms, suitable for electronic cigarettes, electric toys, digital cameras, GPS and other portable devices. This article will analyze the core characteristics, working principles and application design points of the CXLB73279 in depth to help engineers choose the most suitable charging solution in the design.
1. Product Overview
CXLB73279 is a synchronous step-down lithium ion battery charging management chip that supports 4.6V to 26V wide voltage input. It adopts a fixed 550kHz switching frequency and has a charging efficiency of more than 90%, greatly reducing the heating of the chip itself. Its internal integration of 28V high-voltage devices, can effectively resist the surge voltage or the risk of misconnection of high-voltage adapter, with high system security.
The chip uses a small DFN3x3-10L package with few peripheral components, making it ideal for space-constrained portable device applications. Its preset charging voltage accuracy is 1%, supports a complete charging management process, including three stages of current elimination, constant current, and constant voltage, and has functions such as automatic recharging, battery temperature monitoring, and output short circuit protection.
Main characteristics of 2.
· Wide input voltage range: 4.6V ~ 26V, maximum withstand voltage 28V
· High efficiency synchronous buck architecture: Efficiency> 90%, low fever
Maximum 2.5A adjustable charging current
Input current adaptive, suitable for a variety of power adapters
· Built-in power MOS tubeNo need for external diodes
· High precision voltage reference：4.2V±1%
· Dual state indication output（NCHRG/NSTDBY）
Comprehensive protection mechanisms: over-temperature, short circuit, backfilling, undervoltage lockout, etc.
· Ultra-low standby current: Only 20μA in shutdown mode
3. pin function and key circuit design
3.1. Pin profile:
· Wine: Power input, supports up to 26V working voltage
· NCE: enable control, low level is active
· NCHRG/NSTDBY: Charging/full state indication, withstand voltage 28V
· NTCBattery temperature detection, external thermistor
· BAT/VSBattery voltage/current detection, external resistor RS set charging current
· LX: Switch node, connecting external inductor
· GND: Grounding, reliable connection with heat dissipation copper foil
3.2. Charging current setting:
The charging current is determined by the detection resistor RS between VS and BAT, and the formula is:
For example, when the charging current is set to 2.0A, RS takes 33.3 mΩ (which can be realized by parallel resistor).
3.3. Temperature monitoring and protection:
Through an external 10kΩ(25 ℃)NTC thermistor, the chip can monitor the battery temperature in real time. When the NTC pin voltage exceeds the 180mV ~ 1.35V range, charging is suspended to prevent battery damage in high or low temperature environments. If this function is not required, the NTC can be suspended or connected to the ground with a resistor ≥ 1 MΩ.
4. workflow and protection mechanisms
4.1. Charging process:
4.1.1 current elimination charging: When the battery voltage is lower than 2.85V, pre-charge with a small current of about 200mA.
4.1.2 constant current charging: After the battery voltage rises, it enters the fast charging mode, and the current is set by RS.
4.1.3 constant voltage charging: When the battery approaches 4.2V, the current gradually decreases.
4.1.4 Charge termination: When the current drops below the set threshold (such as 200mA), charging ends and NSTDBY outputs a low level.
4.2. Intelligent protection function:
· input adaptive: When the input voltage drops to 4.55V, the charging current is automatically reduced to protect the adapter
· over-temperature protection: When the junction temperature exceeds 145 ℃, the current will automatically drop to prevent overheating damage
· Short circuit protection: When the output is lower than 2.2V, enter the current limiting mode
· Automatic recharge: Restart the charge cycle after the battery voltage drops by 150mV
5. PCB Layout and Thermal Design
Because the CXLB73279 uses DFN small package, heat dissipation mainly relies on PCB copper foil. Recommendations:
· Design 1.7 × 3.0mm thermal pad at the bottom of the chip
· Multiple heat dissipation vias with 0.8mm aperture are arranged and connected to the inner layer or the back copper sheet
· When soldering, tin is filled from the back to ensure a smooth heat dissipation path between the chip and the PCB.
· Avoid arranging other heat sources around the chip to prevent affecting charging performance
6. typical application scenarios
CXLB73279 is widely used in:
· Electronic Cigarettes
· Electric toys, tools
· MP3/MP4 player, digital camera
· GPS navigation equipment, electronic dictionary
· Various types of portable charging equipment and white LED driver (3W ~ 11W)
7. Typical Application Circuit Schematic Diagram
Eight,Conclusion
With its high efficiency, high integration and comprehensive protection, CXLB73279 is an ideal high current battery charging solution in portable devices. Its wide voltage input range and intelligent adaptive mechanism enable it to adapt to a variety of power supply environments to ensure a stable and reliable system. Reasonable PCB layout and heat dissipation design can give full play to its 2.5A continuous charging capability to meet the dual needs of modern electronic equipment for fast charging and small size.
For more technical details or to obtain samples, welcome to visitJTM-IC official website.
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