CXLB73284 is a synchronous switch buck charging management chip with integrated N-MOS power tube. The input voltage range is 5V to 24V, and it supports charging of 1 to 4 lithium batteries. It uses a 1MHz high-frequency switch architecture to effectively reduce the size of peripheral components and significantly reduce the cost of the system BOM. The chip has a programmable charging current (maximum 2A), the charging voltage accuracy is as high as ± 1%, and the charging current accuracy is ± 10%, which effectively guarantees the consistency and safety of the charging process.
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[ CXLB73284 ]"
CXLB73284: highly integrated 1-4 lithium battery synchronous buck charging management chip depth analysis
In the context of the rapid development of portable electronic devices, power tools, Bluetooth audio and other products, an efficient, safe and flexible lithium battery charging management scheme has become an indispensable part of the design. As a high-frequency synchronous buck charging management chip supporting 1-4 lithium batteries, CXLB73284 has a wide input voltage of 5V-24V, a maximum programmable charging current of 2A, a conversion efficiency of up to 93% and a comprehensive system protection mechanism, and is suitable for various multi-string lithium battery application scenarios. This article will comprehensively introduce the technical characteristics, working principle, design points and typical applications of the CXLB73284, and help engineers to realize the design of high-performance charging system.
1. Product Overview
CXLB73284 is a synchronous switch buck charging management chip with integrated N-MOS power tube. The input voltage range is 5V to 24V, and it supports charging of 1 to 4 lithium batteries. It uses a 1MHz high-frequency switch architecture to effectively reduce the size of peripheral components and significantly reduce the cost of the system BOM. The chip has a programmable charging current (maximum 2A), the charging voltage accuracy is as high as ± 1%, and the charging current accuracy is ± 10%, which effectively guarantees the consistency and safety of the charging process.
The chip provides ESOP-8 and DFN -500.00g package forms to adapt to different space and heat dissipation requirements, and is widely used in tablet computers, power tools, Bluetooth speakers, POS machines, wireless walkie-talkies and other equipment.
2. core features
· High frequency synchronous switch architecture: 1MHz switching frequency, effectively reduce the inductor size, improve power density.
· Wide input voltage range5V-24V, adapt to a variety of power input.
· Multi-cell battery support: Set the charging voltage of 1-4 batteries through the CELL pin.
· Programmable charging current: Maximum 2A, flexibly set by external detection resistor.
· High precision charging control: Charging voltage accuracy ± 1%, current accuracy ± 10%.
· Perfect system protection: Integrated output short circuit, over temperature, battery over voltage, charging timeout, NTC temperature protection, etc.
· Intelligent status indication: STAT pin outputs charging status (charging/full/abnormal/sleep).
· Thermal feedback regulation mechanism: Automatic downflow when junction temperature exceeds 125°C, shutdown protection at 155°C.
3. pin function and electrical parameters
The CXLB73284 offers ESOP-8 and DFN -500.00g packages with the following pin functions:
· IN: For power input, an external 1μF ceramic capacitor is required. When the input is higher than 12V, it is recommended to add 100μF electrolytic capacitor.
· CELL: Battery number selection pin, set 1-4 batteries by pulling up and down resistors.
· BAT: Battery voltage detection and charging output need to be connected to 0.1μF filter capacitor.
· CS: Current detection input, external RSNS resistor to set the charging current.
· LX: Switch node, connected to the power inductor.
· STAT: Charging status indication (high resistance/high/low/flashing corresponding to different states).
· TS: NTC temperature detection pin, grounded when not in use.
· BS: Bootstrap capacitor pin, connect 22nF capacitor to LX.
· PGND/AGND: Power ground and analog ground, the bottom pad needs to be well grounded.
Under typical operating conditions, the CXLB73284 can achieve a conversion efficiency of up to 93%, a quiescent current as low as 10 μA (charge complete state), and supports a variety of battery pack charging voltages from 4.2V to 16.8V.
4. charging process and key parameter setting
4.1 charging process
The CXLB73284 adopts the three-stage intelligent charging mechanism of "pre-charging-constant current charging-constant voltage charging:
1. Pre-charge mode: When the battery voltage is lower than the VLOWV threshold, pre-charge with a constant current of 10% to restore the deep discharge battery.
2. Constant current charging: After the battery voltage rises, it enters the constant current stage to set the current for fast charging.
3. Constant voltage charging: When the battery voltage is close to the set value, it turns to the constant voltage mode, and the current gradually decreases until it is fully charged.
4.2 battery count setting
Set the number of battery cells via the CELL pin external resistor:
|
CELL SETTING |
Number of battery section |
Typical full voltage |
|---|---|---|
|
10kΩ pull-down |
Section 1 |
4.2V |
|
float |
Section 2 |
8.35V |
|
50kΩ pull-down |
Section 3 |
12.6V |
|
Pull-up |
Section 4 |
16.8V |
4.3 charging current setting
The charging current is set by the sense resistor RSNS between CS and BAT, and the formula is:
The typical value of VCS-BAT_CC is 30mV. For example, when RSNS = 20 mΩ, the charging current is about 1.5A.
Detailed explanation of 5. protection mechanism
5.1 temperature protection
· thermal feedback regulation: Automatically reduce the charging current when the junction temperature is> 125°C.
· over-temperature shutdown: Stop charging when junction temperature> 155°C.
· NTC Protection: Monitor the battery temperature through an external 10kΩ NTC resistor (B = 3950K) on the TS pin, and suspend charging over the range.
5.2 Security Timer
· Precharge Timer: Up to 60 minutes, overtime will report an error.
· Current Elimination Charge Timer: Continue to run for 40 minutes after charging is terminated to improve battery saturation.
5.3 Other Protection
· Input undervoltage protection: Stop charging when VIN<4.1V.
· Battery short circuit protection: When VBAT<2.2V, enter the low current activation mode.
· Anti-irrigation protection: Prevent reverse discharge of the battery through the VSLEEP threshold.
6. PCB Design Recommendations
To ensure system stability and anti-interference ability, please note:
· The 1μF 0.1μF capacitor at the IN pin should be placed close to the chip, and the ground path is short and thick.
· The BS capacitor should be close to the BS and LX pins, and the traces should be as short as possible.
· CS and BAT pin filter capacitor should be common ground, and good connection with chip ground.
· Shielding inductance with saturation current greater than 2A is selected for power induction.
· The bottom pad should be connected to the underlying ground plane through multiple vias to enhance heat dissipation.
7. typical application scenarios
CXLB73284 widely applicable:
· Power Tools & Garden Equipment
· Tablet PC and portable POS machine
· bluetooth speaker with wireless intercom
· Industrial Handheld Terminal and Testing Equipment
· Multi-cell lithium battery charging base and power module
8. Typical Application Circuit Schematic Diagram
NineConclusion
CXLB73284 with its high integration, high frequency and high efficiency, comprehensive protection mechanism and flexible setting, become the ideal choice for 1-4 lithium battery charging system. Whether it is a portable device with limited space or a high-reliability industrial scenario, the chip can provide a stable, safe and efficient charging management solution. For detailed data sheets, application samples or technical support, please visitJTM-IC.comContact us.
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