CXLB73331 is a linear charge management chip designed for a single lithium ion battery. It is packaged in a thin SOT-23-5L package with few peripheral components and is very suitable for portable devices with limited space. Its input voltage range is 4.25V ~ 6.5V, which can be directly compatible with USB power supply without external MOSFETs, detection resistor and blocking diode, greatly simplifying the system design.
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[ CXLB73331 ]"
CXLB73331: high-performance single-cell lithium battery linear charging management chip, providing a safe and efficient power supply solution for portable devices
With the increasing popularity of mobile devices and portable electronic products, the charging safety, efficiency and integration of lithium batteries have become the key to design. CXLB73331 as a perfect single lithium ion battery constant current/constant voltage linear power management chip, with its small size, high integration, multiple protection mechanisms and excellent temperature adaptability, it has become a mobile phone, PDA, ideal charging solution for Bluetooth devices, MP3 and other products. This article will comprehensively analyze the functional features, working principles, design guidelines and typical applications of CXLB73331 to help engineers realize a safer and more compact battery management system.
I. Product overview and application scenarios
CXLB73331 is a linear charge management chip designed for a single lithium ion battery. It is packaged in a thin SOT-23-5L package with few peripheral components and is very suitable for portable devices with limited space. Its input voltage range is 4.25V ~ 6.5V, which can be directly compatible with USB power supply without external MOSFETs, detection resistor and blocking diode, greatly simplifying the system design.
Main application areas include:
·Mobile communication equipment: mobile phone, interphone, Bluetooth headset;
·Portable entertainment equipment: MP3 player, portable speaker, handheld game machine;
·Smart wearable devices: smart bracelet, watch, Health Monitor;
·IoT devices: Bluetooth beacon, sensor node, portable collection terminal.
II. Core features and technical advantages
2.1. High integration and small size design
CXLB73331 integrates power MOSFETs, current detection and voltage regulation functions, requires only a few peripheral components, and is packaged with SOT-23-5L, which greatly saves PCB area and is suitable for highly integrated portable products.
2.2. Intelligent charging management
Full charging cycle supported: precharge & rarr; Constant current charging & rarr; Constant voltage charging & rarr; Charging cut-off. When the battery voltage is lower than 2.9V, it enters the trickle charging mode to avoid battery damage; When the charging current drops to 1/10 of the set value, it automatically stops charging to prevent overcharging.
2.3. Temperature adaptation and thermal regulation
The chip has built-in thermal feedback mechanism, which automatically reduces the charging current when charging at high ambient temperature or large current, effectively controls the temperature rise and improves the reliability of the system.
2.4. Multiple protection mechanisms
·Battery reverse connection protection: patented structure ensures that the chip enters the protection state when the battery is connected in reverse to prevent IC damage and battery short circuit;
·Input undervoltage lockout: pause charging when the input voltage is lower than 3.8V, protect power system;
·ESD protection: The ESD capability of the human body model is up to 7KV, which improves the antistatic capability of the system.
2.5. Charging status indication
Drive the LED through the CHRG pin or connect to the MCU to display the charging status (charging/full/abnormal) in real time to improve the user experience.
3. Detailed explanation of pin functions
1. CHRG (pin 1)
Open drain output charging status indicator pin. When charging, it outputs a low level and can drive LED; When charging is completed or in the shutdown state, it is in a high resistance state. With the external capacitor, the battery presence detection function can also be realized.
2. GND (pin 2)
System grounding terminal.
3. BAT (pin 3)
The battery connection terminal provides charging current and controls float-charge voltage to stabilize at 4.2V(± 1%). Internal integrated anti-reverse connection protection circuit.
4. VIN (pin 4)
Power input pin, support 4.25V ~ 6.5V DC input, it is recommended to parallel ≥ 1μF capacitor to regulated power supply.
5. PROG (pin 5)
Charging current programming and enable control pin. Set the charging current through ground resistance RPROG:
The typical value of VPROG is 1.0V. This pin can also be used to turn off the charger. When the voltage is higher than 1.21V, it enters the shutdown mode and the input current drops to 25μa.
IV. Workflow and charging curve
The charging process of CXLB73331 is divided into three stages:
·Trickle charging: When the battery voltage is less than 2.9V, charge the battery with a small current of about 1/5 of the set current to restore the deeply discharged battery.
· Constant current charging: When the battery voltage rises to more than 2.9V, it is charged quickly with the set current. At this time, the PROG pin voltage is about 1.0V.
· Constant voltage charging: When the battery voltage is close to 4.2V, it enters the constant voltage mode, and the current gradually drops until the charging is cut off when it drops to 1/10 of the set value.
V. Typical application circuit design
5.1. The following figure shows the typical application circuit of CXLB73331.:
VIN → C1(4.7μF) → GND
VIN & rarr; Chip pin 4
PROG → RPROG → GND
BAT → C2(10μF) → GND
BAT & rarr; Battery positive
CHRG → RLED → LED → VIN
5.2. Design description:
5.2.1C1 is input filter capacitor, 4.7 μF is recommended;
5.2.2C2 is the battery-side energy storage capacitor, 10 μF is recommended;
5.2.3RPROG is selected based on the required charging current, for example:
·500mA charging: RPROG & asymp; 2 Kohm
·200mA charging: RPROG & asymp; 5kohm
5.2.4RLED is the current limiting resistor, which is calculated according to the LED current.
VI. Electrical characteristics and performance parameters
6.1. Absolute maximum rating (TA = 25℃)
·Input voltage:-0.3V to VSS 7V
·BAT voltage:-0.3V to 7V
·Operating temperature:-40℃ ~ 85℃
·Storage Temperature:-65 ℃ to 125 ℃
·Allowable power consumption: 250MW
6.2. Key performance parameters (VIN = 5V,TA = 25℃)
·Float-charge pressure: 4.2V ± 1%
·Adjustable Charging current Range: up to 500mA
·Standby mode battery current:<2.5% A
·Shutdown mode input current: & asymp;25% A
·Trickle charging threshold voltage: 2.9V
·Input undervoltage lockout threshold: 3.8V (with 200mV hysteresis)
VII. PCB layout and heat dissipation suggestions
7.1. Power supply and ground wire processing
·The pin capacitors of VIN and BAT should be as close as possible to the chip;
·The ground plane should be complete to reduce noise interference.
7.2. Heat dissipation design
·At the bottom of the chip, heat dissipation via holes can be added to connect to the bottom layer copper foil;
·Avoid arranging other heating components directly below the chip;
·In high-current charging applications, the PCB plus-sized area can be appropriately copper foil to assist in heat dissipation.
7.3. Signal routing
·PROG pin resistance should be close to the chip, and the wiring is short and thick;
·CHRG indicates that if the output needs long-distance routing, we recommend that the series resistance prevent interference.
8. FAQ and debugging guide
8.1. Inaccurate charging current
Check the RPROG resistance accuracy (1% recommended) and measure whether the PROG pin voltage is about 1.0V.
8.2. Abnormal charging indicator light
Confirm whether the external circuit of the CHRG pin is normal and whether the LED polarity is correct, and try to reduce the RLED resistance value.
8.3. Chip fever is obvious
·Check whether the input voltage is within the recommended range;
·Confirm whether the battery is close to the full state (the current decreases in the constant voltage phase and the power consumption decreases);
·Optimize PCB heat dissipation design.
8.4. Battery reverse connection protection test
When the battery is connected in reverse, the chip should enter the protection state. The BAT pin current is about 0.7mA, which will not damage the chip or battery.
IX. Selection and extended application
CXLB73331 is suitable for most single lithium ion/lithium polymer battery charging scenarios. For larger charging current or multiple battery management, please contactjtm-ic.comGet more model recommendations.
The chip can also cooperate with MCU to realize intelligent charging management, for example:
·Dynamically adjust the charging current through the PROG pin;
·Detect the charging status through the CHRG pin and report it to the system;
·Realize advanced functions such as timing charging and temperature control charging.
10. Conclusion
CXLB73331 provides a reliable, efficient and safe lithium battery charging solution for portable electronic devices with its high integration, multiple protection mechanisms, good temperature adaptability and simple peripheral circuits. Whether it is consumer electronics or industrial equipment, its excellent performance and stability can meet the stringent design requirements.
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