CXLB73333 is A complete linear charging controller for two-cell lithium-ion batteries. Its preset charging voltage is 8.4V (accuracy ± 1%), and the charging current can be programmed by external resistor, up to 0.9A. The chip supports a wide input voltage range (9V-13.5V) and has input overvoltage protection (absolute maximum input voltage 30V). It is compatible with common 12v adapters or USB-PD power supplies. With SOP-8 package and simple peripheral components, it is very suitable for portable devices with compact space.
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[ CXLB73333 ]"
CXLB73333: high-performance double-cell lithium battery linear charging management chip, providing a safe and intelligent charging solution for portable devices
With the increasingly powerful functions of portable electronic devices, double lithium ion batteries have gradually become the preferred power supply scheme for Bluetooth devices, portable players, wireless headphones and other products due to their higher voltage and energy density. CXLB73333 as a high-precision constant current/constant voltage linear charging management chip specially designed for double lithium batteries, it integrates programmable charging current, temperature monitoring, double LED status indication and multiple protection functions, it provides engineers with highly integrated, safe and reliable charging solutions. This article will deeply analyze the technical characteristics, workflow, design points of CXLB73333 and its application in various portable devices.
I. Product overview and core features
CXLB73333 is A complete linear charging controller for two-cell lithium-ion batteries. Its preset charging voltage is 8.4V (accuracy ± 1%), and the charging current can be programmed by external resistor, up to 0.9A. The chip supports a wide input voltage range (9V-13.5V) and has input overvoltage protection (absolute maximum input voltage 30V). It is compatible with common 12v adapters or USB-PD power supplies. With SOP-8 package and simple peripheral components, it is very suitable for portable devices with compact space.
Main application scenarios:
·Bluetooth speaker, wireless headset, walkie-talkie
·Portable media player, handheld game machine
·Smart home equipment, portable tools
·Double-section lithium battery pack mobile power supply, emergency lighting
II. Product advantages and functional highlights
2.1.High precision voltage and current control
The charging voltage accuracy is as high as ± 1% to ensure that the battery is fully charged. The charging current is flexibly set by external detection resistor (RSET) to meet the needs of batteries of different capacities.
2.2.Complete charging management process
Supports pre-processing charging (trickle charging) & rarr; Constant current charging & rarr; Full cycle management of constant voltage charging, with charging termination (current drops to the set threshold) and automatic recharging functions.
2.3.Integrated temperature monitoring and protection
The external NTC thermistor monitors the battery temperature in real time to ensure that the charging process is only carried out within a safe temperature range, and the internal overheating shutdown protection (TSD & asymp; 150 ℃) is provided.
2.4.Dual LED charging status indication
The CHRG1 and CHRG2 pins can drive dual LEDs to clearly indicate different charging states (charging, full charge, abnormal temperature, no battery, etc.), improving user experience.
2.5.Multiple protection mechanisms
·Input overvoltage lock (OVLO)
·Abnormal battery temperature protection
·Minimum input-output voltage difference monitoring (avoid inverse current)
·Optional reverse blocking diode protection
3. Detailed explanation of pin functions
| Pin | Name | Function description |
|---|---|---|
| 1 | CHRG1 | Charging status indication 1 (often low charging) |
| 2 | TS | Temperature detection, external NTC thermistor |
| 3 | GND | Systematically |
| 4 | VOUT | Charging current output, connected to the positive electrode of the battery |
| 5 | PDRI | External PMOS driver |
| 6 | CS | Current detection and programming terminal, connected to detection resistor |
| 7 | CHRG2 | Charging status indication 2 (always low when full) |
| 8 | VIN | Power input (9v‑13.5V) |
IV. Working principle and charging process
The charging process of CXLB73333 is strictly controlled by the internal state machine, and its workflow is as follows:
4.1 Power-on and temperature detection: After the input voltage is normal, the TS pin voltage is detected. If the temperature is within the allowable range (vts‑cold> VTS> vts‑hot), continue.
4.2 pretreatment charging: if the battery voltage is lower than the trickle charging threshold (VTRIKL & asynmp; 6.3V), trickle charging is carried out with a set current of about 15% to restore the deep discharge battery.
4.3 constant current charging: After the battery voltage rises to the normal range, it enters the constant current charging stage. The current is set by RSET:
ICHG= VCS/RSET(The typical value of VCS is 200mV).
4.4 Constant voltage charging: When the battery voltage is close to 8.4V, turn into constant voltage charging mode, and the current gradually decreases.
4.5 charging termination: When the charging current drops to about 10% of the set value, it is determined to be full and the charging is stopped.
4.6 automatic recharging: if the battery voltage drops more than the recharge hysteresis voltage (& Delta;VRCH & asynmp; 80mV), restart the charging cycle automatically.
V. Typical application circuit design
5.1. The following figure shows the typical application circuit of CXLB73333, which is suitable for most two-cell lithium battery charging scenarios:
VIN(9V‑13.5V)───┬── C1(20µF) ─── GND
── R1(2 kΩ) ── LED1 ── CHRG1
── R2(2 kΩ) ── LED2 ── CHRG2
── chip pin 8
CS (pin 6) ── RSET (for example, 0.5 Ω) ── VIN
VOUT (pin 4) -- -- C2(20 & micro;F) -- -- GND
── external PMOS (optional)
── battery positive (BAT)
TS (pin 2) ── NTC thermistor (10kΩ) ── GND
5.2 Suggestions on selection of key components:
· RSET: calculated according to the required charging current, for example, 0.9A can be charged by 0.22 Ω (accuracy 1%).
· Input/output capacitor: it is recommended to use 20 & micro;F low ESR Capacitor to ensure stable power supply.
· NTC thermistor: 10kΩ(25℃) is recommended, which is close to battery installation.
· LED current limiting resistor: Usually 2 kΩ, adjusted according to LED current.
VI. Electrical characteristics and performance parameters
6.1. Absolute maximum rating
·Input voltage VIN:-0.3V to 30V
·Working environment temperature:-40℃ ~ 85℃
·Storage Temperature:-65 ℃ to 125 ℃
·Maximum power consumption PD:2W (pay attention to heat dissipation design)
6.2. Key electrical parameters (TA = 25℃,VIN = 12V)
·Output voltage (constant voltage stage):8.4V ± 1%
·Charging current setting Range: up to 0.9A
·Trickle charging threshold voltage: 6.3V
·Input quiescent current (standby): about 4mA
·Sleep current (VIN = 0): about 25 & micro;A
·Temperature detection threshold:
♦ COLD threshold vts‑cold: 2.4V
♦ thermal threshold vts‑hot: 0.5V
VII. PCB layout and heat dissipation design guide
7.1.Key points of layout
·The input capacitor C1 and the output capacitor C2 should be as close as possible to the corresponding pin of the chip.
·CS detection resistor should be close to the chip, and the routing line should be short and thick to reduce noise interference.
·NTC thermistor should be close to the battery surface, and the routing should not be parallel to the power line.
7.2.Heat dissipation suggestions
·At the bottom of the chip, heat dissipation via holes can be added to connect to the internal or back copper layer.
·If external PMOS is used, ensure that it has a good heat dissipation path.
·In the continuous high-current charging scenario, it is recommended to evaluate the actual heat dissipation requirements through the temperature rise curve (see figure 3).
7.3.Noise and EMI considerations
·The power ground is separated from the signal ground, with a single point of connection.
·Sensitive signal lines (such as TS and CS) are far away from high-frequency switch nodes.
8. Common Application problems and debugging suggestions
8.1.The charging current is not up to standard.
·Check RSET resistance value and accuracy.
·Measure whether the CS pin voltage is about 200mV.
·Check whether the input voltage is enough higher than the battery voltage (about 600mV minimum differntial pressure).
8.2.LED indication exception
·Check the CHRG1/CHRG2 level against the status table.
·Confirm that the LED and current limiting resistor are connected correctly.
·Check whether the battery is well connected.
8.3.Chip overheating protection
·Check whether the charging current is too large.
·Optimize PCB heat dissipation design to ensure environmental ventilation.
·Check whether the battery temperature is within the allowable range.
8.4.Unable to enter the charging state
·Check whether the input voltage is between 9v-13.5v.
·Check whether the TS pin voltage is between 0.5V and 2.4V.
·Check whether the battery has been released or damaged.
IX. Selection and extended application
CXLB73333 is suitable for most dual lithium ion/polymer battery charging scenarios. If you need higher charging current, wider input voltage, or more battery series solutions, you can accessjtm ‑ic.comGet full range of power management chip selection support.
The chip can also cooperate with MCU to realize:
·Dynamic monitoring and recording of charging process
·Multi-segment current regulation charging
·Battery Health status (SOH) assessment
·System-level power consumption management and wake-up control
10. Conclusion
CXLB73333 provides a reliable, safe and efficient solution for charging double lithium batteries with its high precision, high integration, comprehensive protection mechanism and clear user instructions. Whether it is consumer audio equipment, portable players, industrial control instruments and emergency equipment, CXLB73333 can help designers improve product performance and user experience, shorten development cycle and reduce system costs.
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