CXLB73291 is a working voltage range of 2.75V to 6.5V PFM boost type dual lithium battery charging control chip. Its internal integrated reference voltage source, inductor current detection unit, battery voltage detection circuit, on-chip N-MOSFET and other key modules, fewer external components, simple circuit, greatly reducing the complexity and cost of the system.
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[ CXLB73291 ]"
CXLB73291: high efficiency PFM boost dual lithium battery charging control chip
With the increasing popularity of portable electronic devices, efficient, safe and flexible battery charging management solutions have become the core of product design. As a PFM boost dual-section lithium battery charging control integrated circuit, CXLB73291 is widely used in POS machines, electric fans, audio and independent chargers with its wide input voltage range, high integration, intelligent charging management and multiple protection functions. And other scenes. This article will comprehensively analyze the technical characteristics, working principle, design points and typical applications of the CXLB73291 to help engineers achieve efficient and reliable charging system design.
1. Product Overview: Efficient and Flexible Charging Control Solution
CXLB73291 is a working voltage range of 2.75V to 6.5V PFM boost type dual lithium battery charging control chip. Its internal integrated reference voltage source, inductor current detection unit, battery voltage detection circuit, on-chip N-MOSFET and other key modules, fewer external components, simple circuit, greatly reducing the complexity and cost of the system.
The chip is packaged in DFN3 * 3-12, supports a switching frequency of up to 1MHz, and has an input power adaptive function, which is especially suitable for solar power supply scenarios. Its unique quasi-constant voltage charging mode can effectively compensate for the voltage loss caused by the internal resistance of the battery and the resistance of the connecting line, and improve the charging efficiency and battery life.
2. core features: the perfect integration of performance and intelligent management
CXLB73291 excellence in performance, security and adaptability:
· Wide input voltage range2.75V-6.5V, compatible with a variety of power inputs, including adapters and solar panels.
· High efficiency PFM control: Supports up to 1MHz switching frequency to improve conversion efficiency and system response speed.
· Quasi-constant voltage charging mode: Automatically switch to low current charging when the battery is close to full charge to optimize the charging curve.
Multiple protection mechanisms: Including die over-temperature protection, current detection resistor short-circuit protection, battery over-voltage protection, etc.
· Intelligent status indication: Output charging status through STAT pin, support LED or MCU interface.
· Low power design: The static operating current is only 280 μA, and the off current is as low as 2 μA.
3. application areas: widely adapted to a variety of electronic devices
The efficiency and flexibility of the CXLB73291 make it perform well in the following scenarios:
· POS machine and portable terminal: Provide stable and fast charging support, adapt to frequent mobile use.
· Electric fans and small appliances: Support high power output (up to 35W) to meet the needs of power equipment.
· Audio equipment: Low noise design and high switching frequency ensure undisturbed sound quality.
· Independent charger with solar charger: Input adaptive function makes it perfectly adapted to unstable power supplies.
4. working principle: multi-stage charging and intelligent protection mechanism
CXLB73291 uses a multi-stage charging strategy to ensure battery health and system safety:
4.1. Constant current charging stage
When the battery voltage is lower than 8.4V, the chip quickly charges the battery with a constant current. The inductor current is set by the external detection resistor RCS, and the upper and lower limits are:
4.2. Quasi-constant voltage charging phase
When the battery voltage reaches 8.4V for the first time, the system turns to the quasi-constant voltage mode, and the charging current drops significantly to avoid overcharging and compensate for the internal resistance drop.
4.3. Charge cut-off and recharge
Charging ends when the battery voltage reaches 8.4V again; automatically restarts the charging cycle when the voltage falls back to 8.0995V.
4.4. Abnormal state protection
Battery low voltage/short circuit protection: Realize step-down small current charging through external P-MOSFET.
· over-temperature protection: Turn off the power tube when the junction temperature exceeds 145 ℃, cool down to 127 ℃ and then recover.
· Detection resistance short circuit protection: If the short circuit lasts for more than 70μ seconds, it is locked and turned off, and it needs to be powered on again or CE reset.
5. Design Guide: Key Parameters and Selection Recommendations
5.1. Charging current setting
by RCSThe resistor sets the average inductor current, which in turn controls the charging current:
In which IL=0.105/RCS, & eta; Take 80% ~ 90%.
5.2. Inductance and frequency calculation
The recommended inductance value is 3.3-15 μH, and the saturation current needs to be higher than the peak current of the system. the formula for the calculation of the switching frequency:
A frequency range of 300-600kHz is recommended to balance efficiency with size.
5.3. Capacitor Selection
· Input capacitor C1: 4.7-47 μF low ESR ceramic capacitor to suppress input ripple.
· Output Capacitor Co: According to the ripple requirements, the X7R/X5R ceramic capacitor with low ESR is recommended.
5.4. Diode and MOSFET Selection
· D1/D2Low-dropout Schottky diodes (e. g. SS24/SS34) are preferred.
· External P-MOS: Only use when battery low-voltage protection is required. Models such as A04435 and A04407A are recommended.
6. PCB Layout and Thermal Recommendations
Good layout is the key to system stability:
· Power and ground: Using wide and short traces, PGND and GND are connected to a large area of copper after being grounded at points.
· critical loop: LX, inductor and diode circuits should be as compact as possible to reduce EMI and switching losses.
· Heat dissipation design: The bottom of the chip is in full contact with the PCB copper skin, and is connected to the bottom ground through vias to enhance heat dissipation.
7. Typical Problems and Solutions
· The charging current is not up to standard: Check the RCS resistance and input voltage, and confirm that the CE pin is high.
· STAT indicator lamp is abnormal: Check whether the battery voltage is abnormal (lower than 2V or higher than 8.65V), or the protection circuit is triggered.
· Chip overheating: Optimize heat dissipation design, reduce charging current or enhance PCB thermal conductivity.
· Adapted solar input unstable: Use the chip's adaptive loop to automatically adjust the input current to adapt to the power supply capability.
8.Package and pin function
Nine, typical application schematic diagram
TenConclusion: the choice of JTM-IC, quality and technology double guarantee
CXLB73291 with its high integration, flexible input adaptability and comprehensive protection function, become the ideal choice of dual lithium battery charging system. As a JTM-IC (jtm-ic.com) is one of the core products, we are committed to providing customers with high-performance chip solutions and professional technical support. For more product details, design resources or sample application, please visit the official websitejtm-ic.comTogether with us, we promote innovation and upgrading.
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