CXLB73285 is a synchronous buck charging management chip with built-in power MOS, with a wide input voltage range of 4.5V to 26V, suitable for various input sources such as adapter, USB PD, vehicle power supply, etc. Its switching frequency is 250kHz, the conversion efficiency is up to 95%, it supports charging of 1~4 strings of lithium batteries, the charging current is up to 3A, and the charging parameters can be flexibly set through an external resistor or I2C interface.
-
[ CXLB73285 ]"
CXLB73285: high performance adjustable multi-string lithium battery charging management IC comprehensive analysis
With the continuous improvement of battery performance requirements for portable electronic devices, power tools, energy storage systems, etc., an efficient, flexible and safe lithium battery charging management scheme has become the key to the design. As a highly integrated synchronous switch step-down charging management IC, CXLB73285 supports charging of 1~4 strings of lithium batteries/lithium ion batteries, with adjustable charging current up to 3A, comprehensive protection mechanism and flexible I2C control function, and is widely used in various multi-string battery charging scenarios. This article will provide an in-depth introduction to the core features, working principles, design points and typical applications of the CXLB73285, providing engineers with a complete reference design guide.
1. Product Overview
CXLB73285 is a synchronous buck charging management chip with built-in power MOS, with a wide input voltage range of 4.5V to 26V, suitable for various input sources such as adapter, USB PD, vehicle power supply, etc. Its switching frequency is 250kHz, the conversion efficiency is up to 95%, it supports charging of 1~4 strings of lithium batteries, the charging current is up to 3A, and the charging parameters can be flexibly set through an external resistor or I2C interface.
The chip is packaged in QFN24, which has good heat dissipation performance and compact layout advantages, and is suitable for application scenarios with limited space.
Main characteristics of 2.
· Wide input voltage range: 4.5V ~ 26V, adapt to a variety of power input.
· Multi-string battery support: Flexible setting of 1~4 series battery charging voltage through FB pin external resistor.
Adjustable charging current: Support independent current limiting of battery terminal and input terminal, maximum 3A output.
· NTC temperature protection: External NTC resistor to realize charge and discharge temperature monitoring and protection.
Input undervoltage and overvoltage protection: Support peripheral undervoltage point, adjustable overvoltage protection threshold.
· I2C programming control: Supports register configuration of charging parameters, protection thresholds and LED status.
· Comprehensive system protection: Including output short circuit, over current, over temperature protection, ESD 4kV.
3. Pin Function and Electrical Characteristics
CXLB73285 using QFN24 package, the main pin functions are as follows:
· WINE/WINEPower input and input voltage detection.
· ICHG/IADP: The external resistor sets the charging current of the battery terminal and the input terminal.
· FB: Output voltage feedback, used to set the number of battery strings and full voltage.
· NTC: External NTC resistance to achieve temperature detection.
· SCL/SDAI2C communication interface for register configuration.
· LX: Switch node, connected to the power inductor.
· VSYS: system output, need external 22μF ceramic capacitor.
· EPAD: The heat dissipation ground shall be well grounded to improve the heat dissipation performance.
Under typical working conditions (VIN = 12V,VBAT = 3.7V), the CXLB73285 can achieve a charging current of up to 3A, a current elimination charging current of about 100mA, and high constant voltage charging accuracy, meeting the charging requirements of various battery types.
4. charging process and parameter setting
The CXLB73285 adopts the classic "eliminating current-constant current-constant voltage" three-stage charging mechanism:
1. Current elimination charging: When the FB voltage is lower than 1.5V, pre-charge the battery with a current of about 100mA.
2. Constant current charging: After the FB voltage rises, it is quickly charged with a set constant current (such as 3A).
3. Constant voltage charging: When the FB voltage is close to the set value (such as 2.1V), it turns to the constant voltage mode, and the current gradually decreases until it is full.
4.1 battery type and full voltage setting
The number of battery strings and full voltage can be set through external resistors RFB1 and RFB2 of FB pin, and the relationship is as follows:
|
RFB1 |
RFB2 |
full voltage |
Number of battery strings |
|---|---|---|---|
|
100K |
100K |
4.2V |
1 string |
|
100K |
300K |
8.4V |
2 strings |
|
100K |
500K |
12.6V |
3 strings |
|
100K |
700K |
16.8V |
4 strings |
In order to ensure accuracy, RFB1 and RFB2 should use 0.1% accuracy resistors.
4.2 charging current setting
The CXLB73285 supports setting the charging current of the battery terminal and the input terminal respectively through the external resistor of ICHG and IADP pins:
· Battery terminal current: ICHG is connected to RICHG, and the formula isICC_BAT = 75K / RICHG
· Input current: IADP to RIADP, the formula isICC_ADP = 75K / RIADP
The actual charging current is the smaller of the two to ensure that the adapter is not pulled. If you want to limit the current at the battery terminals only, set RIADP to 0Ω and vice versa.
5. NTC temperature protection mechanism
CXLB73285 through the NTC pin external NTC resistance and fixed resistance to form a voltage divider network, to achieve temperature detection and protection:
· Normal range:-10 ℃ ~ 45 ℃, normal charging.
· high temperature downflow:>45 ℃, charging current is halved.
· High temperature stop charging:>60 ℃, stop charging.
If no NTC is required, ground the NTC pin through a 51kΩ resistor.
6. I2C control function
6.1. The CXLB73285 supports I2C interface, and the device address is 0xEA (write)/0xEB (read), which can be used to configure the following parameters:
· Charging Enable/Disable（SYS_CTL1）
· Input overvoltage protection threshold（VINOV_SET）
· NTC Temperature Threshold（NTC_CTL）
· Charging current of battery terminal and input terminal(BAT_ISET / VIN_ISET)
· LED indicator status（LED_REG）
6.2. Note when using I2C:
· SCL/SDA must be high at power-up to enter I2C mode.
· A NACK signal must be sent to read the end of the data.
· Reserved registers are not writable.
7. PCB Design Recommendations
To ensure system stability and EMI performance, please note:
· The VIN pin must be connected to a 100 μF electrolytic or solid state capacitor.
· The VSYS pin needs to be placed in close proximity to the chip with a 22 μF ceramic capacitor.
· The rated current of the power inductor shall be greater than 1.5 times the charging current.
· The EPAD must be connected to the underlying ground plane through multiple vias to enhance heat dissipation.
8. typical application scenarios
CXLB73285 applies:
· Electric Tools and Garden Machinery
· Portable Medical Equipment
· Drone and Robot Battery Systems
· Industrial Handheld Terminal
· Multi-string lithium battery charging stand
9. Application Schematic Diagram and BOM
9.1. Application Schematic Diagram
TenConclusion
With its highly integrated, flexible current and voltage settings, comprehensive protection mechanism and I2C programmability, CXLB73285 is an ideal choice for multi-string lithium battery charging systems. Whether it is a standard application or a customized scenario, the chip can provide an efficient and reliable charging management solution. For more technical details, sample applications or reference designs, please visitJTM-IC.comGet professional support.
Eleven, the relevant chip selection guide download ► More similar products....
