CXLB73286 is a step-down charging management chip designed for multi-string lithium batteries, with built-in power MOSFET, synchronous switching architecture, switching frequency up to 450kHz, and typical conversion efficiency up to 93%. Its input voltage range is as wide as 15V to 24V, supports external resistor to adjust the input undervoltage protection point, and has perfect NTC temperature protection, soft start, input overvoltage/undervoltage protection, over-temperature protection and other multiple protection mechanisms to ensure the safety and reliability of the system.
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[ CXLB73286 ]"
CXLB73286: high efficiency synchronous step-down type 3 string lithium battery charging management IC detailed explanation
In modern electronic equipment, lithium batteries are widely used because of their high energy density and long life. In order to meet the high efficiency and safe charging requirements of multi-string lithium battery pack, the CXLB73286 came into being. This is a high-performance IC with integrated synchronous switching buck converter and charge management function. It is suitable for 2-4 series lithium battery charging systems, especially in scenarios with high requirements for input voltage adaptability and charging efficiency. This article will analyze the characteristics, working principle, typical application and design points of the CXLB73286 in depth to help engineers better understand and select the chip.
1. Product Overview
CXLB73286 is a step-down charging management chip designed for multi-string lithium batteries, with built-in power MOSFET, synchronous switching architecture, switching frequency up to 450kHz, and typical conversion efficiency up to 93%. Its input voltage range is as wide as 15V to 24V, supports external resistor to adjust the input undervoltage protection point, and has perfect NTC temperature protection, soft start, input overvoltage/undervoltage protection, over-temperature protection and other multiple protection mechanisms to ensure the safety and reliability of the system.
The chip standard supports 3 strings of lithium battery charging, the constant current charging current is 1.5A, and the maximum 3A charging current version can be customized according to customer needs. The package form is ESOP8, which has good heat dissipation performance and soldering reliability.
Main characteristics of 2.
· High efficiency synchronous buck architecture: Built-in upper and lower tube power MOS, low on-resistance, efficiency up to 93%.
· Wide input voltage range: 15V ~ 24V, adapt to a variety of adapters or DC power input.
· Customizable charging current: Standard 1.5A, maximum support 3A, to meet the needs of different capacity batteries.
· NTC temperature protection: External NTC resistor to realize temperature monitoring and protection during charging.
Input undervoltage protection: Set the undervoltage protection threshold through the VINSEN pin external resistor to prevent the adapter from overloading.
· Charging status indication: LED pin outputs the charging status for easy user identification.
· Comprehensive protection function: Including input overvoltage, undervoltage, over temperature protection, ESD antistatic capacity up to 4kV.
3. pin function and electrical parameters
The CXLB73286 uses an 8-pin ESOP package, and the functions of each pin are as follows:
· VSYS: System voltage pin, external 22μF ceramic capacitor required.
· Winepower input pin.
· FINSInput voltage detection and enable control pin.
· LED: Charging status indicator drive output.
· NTC: External NTC resistance to achieve temperature detection.
· FB: Output voltage feedback pin, used to set the charge termination voltage.
· BST: The bootstrap capacitor pin is used to drive the upper MOS.
· LX: Switch node, connected inductor.
· EPAD: Heat dissipation ground and power ground shall be well grounded.
In terms of electrical characteristics, the CXLB73286 can realize 1.5A constant current charging under typical working conditions (VIN = 20V,VBAT = 10.8V), the current elimination charging current is about 70mA, and the recharging threshold is 2.05V. Its switching frequency is stable at 450kHz and has good anti-interference performance.
4. working principle and charging process
The CXLB73286 adopts the classic "eliminating current-constant current-constant voltage" three-stage charging mode:
4.1. current elimination charging: When the battery voltage is lower than the current elimination threshold (typically 1.5V), pre-charge with a small current (about 70mA) to restore the deeply discharged battery.
4.2. Constant current charging: After the battery voltage rises, it enters the constant current charging stage to quickly charge at the set maximum current (such as 1.5A).
4.3. Constant voltage charging: When the battery voltage is close to the set value (such as 12.6V), it will switch to constant voltage mode, and the current will gradually decrease until it is fully charged.
If the battery voltage drops below the recharge threshold after full charge, the IC automatically restarts the charging process to ensure that the battery is always in optimal condition.
5. NTC temperature protection mechanism
CXLB73286 support external NTC resistance to achieve temperature monitoring. When the temperature is detected in the range of -10 ℃ to 45 ℃, normal charging; when the temperature exceeds 45 ℃, the charging current is halved; when the temperature exceeds 60 ℃, the charging is stopped. If there is no NTC function requirement, the NTC pin shall be grounded through a 51kΩ resistor and shall not be suspended.
6. PCB Design and Application Suggestions
In order to ensure system stability and EMC performance, design attention should be paid:
· The VSYS pin must be placed in close proximity to the chip with a 22 μF ceramic capacitor and cannot be replaced with an electrolytic capacitor.
· FB voltage dividing resistor (RFB1, RFB2) shall be selected with 0.1% precision resistor to ensure accurate charging voltage.
· The power inductor with rated current greater than 1.5 times the charging current is selected for the electric induction.
· The EPAD shall be connected to the underlying ground plane through multiple vias to enhance heat dissipation.
In a typical application circuit, the VINSEN external voltage dividing resistor sets the input undervoltage protection point, and the NTC pin is externally connected with a 100kΩ NTC resistor and an 82kΩ fixed resistor to form a voltage dividing network to realize accurate sensing of the battery temperature.
7. typical application scenarios
CXLB73286 is widely used in:
· Power tool battery pack
· Portable Medical Equipment
· Battery Management System for Unmanned Aerial Vehicle and Model Aircraft
· Industrial Handheld Devices
· Multi-function charging base
8. epilogue
With its high efficiency, high integration and comprehensive protection functions, CXLB73286 become the ideal choice for multi-string lithium battery charging management. Its flexible customization capabilities (e. g. charging current, number of battery strings) further expand the application range. For more technical details or application samples, welcome to visitJTM-IC.comGet the latest datasheet and technical support.
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