CXLB73321 is a charge management integrated circuit based on synchronous buck architecture, suitable for multiple lithium batteries or lithium iron phosphate batteries. The chip presets three (12.6V) and four (16.8V) lithium battery charging modes, and also supports the flexible setting of the output voltage through the peripheral voltage divider resistor to meet the charging requirements of different battery systems. It adopts 300kHz fixed switching frequency, high charging efficiency, low calorific value, and integrates multiple functions such as input under-voltage protection, output short-circuit protection, and battery temperature protection to ensure safe and reliable operation of the system under various working conditions.
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[ CXLB73321 ]"
CXLB73321 multi-section lithium battery charging management IC comprehensive analysis
With the continuous improvement of battery capacity and charging efficiency requirements for portable devices, power tools and industrial medical equipment, efficient and intelligent multi-cell lithium battery charging solutions have become a market demand. As a high-performance charge management chip that supports multi-type, multi-cell lithium batteries and lithium iron phosphate batteries, CXLB73321 has become an ideal choice for many high-performance applications with its high-precision voltage control, multiple safety protections and flexible output configuration. This article will introduce the CXLB73321 from the product characteristics, working principle, design guide to typical applications, and help engineers to achieve safer and more efficient charging system design.
First, product overview
CXLB73321 is a charge management integrated circuit based on synchronous buck architecture, suitable for multiple lithium batteries or lithium iron phosphate batteries. The chip presets three (12.6V) and four (16.8V) lithium battery charging modes, and also supports the flexible setting of the output voltage through the peripheral voltage divider resistor to meet the charging requirements of different battery systems. It adopts 300kHz fixed switching frequency, high charging efficiency, low calorific value, and integrates multiple functions such as input under-voltage protection, output short-circuit protection, and battery temperature protection to ensure safe and reliable operation of the system under various working conditions.
Second, the core characteristics
2.1. Wide input voltage range: Support 6.8V ~ 28V input, adapt to a variety of power adapters.
2.2. High precision output voltageVoltage control accuracy of ± 1%, to meet the strict charging requirements of lithium batteries.
2.3. Multi-mode output configuration.：
· SEL ground: three lithium battery mode (12.6V)
· SEL high: four lithium battery mode (16.8V)
· SEL suspended: external voltage divider resistor setting output, supports any voltage in the range of 5V to VIN
2.4. Intelligent charging management: With current elimination charging, constant current charging, constant voltage charging and re-charging function.
2.5. Improved status indication: NCHRG (charging) and NSTDBY (charging complete) dual open drain output.
III. Comprehensive protection mechanisms：
· Input Undervoltage Lockout (UVLO)
· Battery Temperature Monitoring (NTC)
· Soft start limiting inrush current
· Anti-battery backfilling design
Four, pin function introduction
| Pin | Name | Function Description |
|---|---|---|
| 1 | DRV | External PMOS gate drive, voltage clamp at VIN-6.3V |
| 4 | NCHRG | Charging status indication (active low) |
| 5 | NSTDBY | Charging complete indication (active low) |
| 6 | NTC | External thermistor for temperature protection |
| 7 | SEL | Charging voltage mode selection |
| 9 | FB | Voltage feedback to regulate the output voltage |
| 10-11 | ISN/ISP | Current detection resistor access terminal |
Fifth, the working principle and charging process
The CXLB73321 uses a typical constant current-constant voltage (CC-CV) charging strategy, and adds a pre-charge and temperature monitoring link:
5.1. Current elimination and pre-charging: When the battery voltage is lower than the preset current elimination threshold (e.g. 8.4V in the three-section mode), the chip pre-charges the battery with a smaller current (e.g. 550mA) to avoid damage to the deep battery.
5.2. Constant current charging: After the battery voltage rises, it enters the constant current mode, and the charging current is set by the external current detection resistor RS:
5.3. Constant voltage charging: When the battery voltage is close to the set float voltage, it will automatically switch to constant voltage mode, and the current will gradually drop.
5.4. Charge termination and recharge: When the current drops to the termination threshold (such as 200mA), the charging ends; if the battery voltage drops more than the recharge threshold, automatically start a new round of charging.
Six, the key design guide
6.1. Charging current setting
By connecting the current detection resistor RS between ISP and ISN, the charging current can be accurately set. For example:
|
RS (Ω) |
IBAT (A) |
|---|---|
|
0.1 |
1.2 |
|
0.05 |
2.4 |
|
0.033 |
3.6 |
6.2. Output voltage setting
· Preset Mode: Select the voltage of three/four lithium batteries through the SEL pin.
· External adjustment mode(SEL is suspended): set by R4 and R5 partial pressure, and the formula is:
R4 R5 > 1MΩ is recommended to ensure stability.
6.3. Temperature monitoring design
NTC pin external 10kΩ(25 ℃) negative temperature coefficient thermistor, internal comparator setting:
· Upper threshold & asymp; 1.46V (about 52 ℃)
· Lower threshold & asymp; 0.19V (about 1 ℃)
Pause charging beyond this range to ensure battery safety.
6.4. Recommendations for selection of external components
· Power PMOS: Select the low VGS model and use the internal grid voltage clamp (& asymp;6.5V) to ensure safety.
· Inductance L: Recommended 10-20 & micro;H shielding power inductor, rated current needs to be greater than charging current.
· Input/output capacitance: Using low ESR ceramic capacitors, input recommended 22 & micro;F above, output 10-22 & micro;F.
· Freewheeling and anti-backfill diode: It is recommended to use a Schottky diode, the withstand voltage is higher than VIN, and the current capacity is greater than the charging current.
Seven, typical application scenarios
· Electric tools: Support 3-4 lithium battery packs for fast charging
· Laptops and Portable Devices
· Industrial and Medical Portable Equipment
· Multiple lithium battery/lithium iron phosphate battery charger
Eight, the conclusion
With its high integration, flexible voltage configuration, comprehensive protection mechanism and high efficiency synchronous buck architecture, CXLB73321 provides a reliable solution for multi-cell lithium battery charging system. Whether in power tools, laptops or industrial medical equipment, the chip helps developers build safe, efficient and compact charging modules. For more technical details, sample applications or complete design information, please visitJTM-IC official website.
Nine, the relevant chip selection guide download ► More similar products....
