CXLB73278 is a synchronous step-down lithium ion battery charging management chip based on a fixed frequency of 550kHz. It is specially designed for 5V adapter environment. The input working voltage is up to 6.0V and The withstand voltage is up to 28V, excellent anti-surge and misconnection protection capability. Its charging efficiency exceeds 90% and its calorific value is extremely low, effectively improving the overall reliability of the system.
-
[ CXLB73278 ]"
CXLB73278: high efficiency 2.5A Li-ion battery charger designed for 5V adapter
With the rapid development of various portable electronic devices, efficient, safe and small-volume battery charging management chips have become the key components in the design. CXLB73278 is A 2.5A Li-ion battery charger chip optimized for 5V AC adapter. It adopts synchronous step-down architecture and integrates multiple protection functions. It is suitable for digital cameras, electronic cigarettes, electric toys and other portable devices. This article will comprehensively introduce CXLB73278 from features, working principles, design points to typical applications to help engineers achieve more reliable and efficient charging solutions.
I. Product Introduction
CXLB73278 is a synchronous step-down lithium ion battery charging management chip based on a fixed frequency of 550kHz. It is specially designed for 5V adapter environment. The input working voltage is up to 6.0V and The withstand voltage is up to 28V, excellent anti-surge and misconnection protection capability. Its charging efficiency exceeds 90% and its calorific value is extremely low, effectively improving the overall reliability of the system.
The chip integrates complete charging management functions, including three-stage charging of current elimination, constant current and constant voltage, supports external resistance to adjust the charging current, and the maximum continuous output current reaches 2.5A. With a DFN3x3-10L package, there are few peripheral components, which greatly saves PCB area and is an ideal choice for space-constrained applications.
II. Core features
· Input voltage range: 4.0V ~ 6.0V, withstand voltage 28V
· Synchronous step-down Architecture: efficiency> 90%, built-in power MOS tube
· Maximum 2.5A output current, external resistance adjustable
· High precision output voltage: 4.2V ± 1%
· Two-way open-circuit drain status indication(NCHRG/NSTDBY)
· Input undervoltage/overvoltage protection, adapter adaptive
· Battery temperature monitoring, supports NTC thermistor
· Soft start, short circuit protection, automatic recharge
· Ultra-low shutdown current: 20% A
3. Pin functions and design points
3.1. Main pin description:
· VIN: power input, support 4.0V ~ 6.0V working voltage
· NCE: enable control, low-level effective
· NCHRG/NSTDBY: Charging/full status indication, withstand voltage 28V
· NTC: battery temperature detection input
· BAT/VS: battery voltage/current detection, external RS set charging current
· LX: switch node, connecting external inductance
· GND: The grounding terminal must be reliably connected to the heat dissipation pad.
3.2. Charging current setting:
The charging current is set by the detection resistor RS between VS and BAT. The formula is as follows:
For example, when the current is set to 2.0A, RS takes 33.3 MΩ (which can be realized by parallel standard resistance).
3.3. Temperature monitoring and protection:
Through the external 10kΩ(25℃)NTC thermistor, the chip can detect the battery temperature in real time. When the voltage of the NTC pin is lower than 180mV or higher than 1.35V, the charging is suspended to prevent the battery from being damaged at extreme temperatures. If this function is not required, the NTC can be suspended or connected to the ground with a resistance greater than or equal to 1 Mohm.
3.4. Pin description
VIN (pin 1): The input voltage terminal, the maximum withstand voltage of this terminal is 28V, and the charging working voltage is 4.2~6.0V.
VGC (pin 2): the gate voltage clamp of the internal drive tube, which is a 0.1uF capacitor indirect to VIN.
NCHRG (pin 3): the charging status indicator. When the charger charges the battery, the pin is pulled to a low level by the internal switch, indicating that the charging is carried out.
Otherwise, the pin is in the high resistance state.
NSTDBY (pin 4): indicates the completion of charging. When the battery is charged, the pin is pulled to the low level by the internal switch, indicating that the charging is completed, no
The pin is in the high resistance state.
NCE (pin 5): Enables the control terminal. Input low level will make the chip in normal working state; Input high level will make the chip card be prohibited from charging state
. The NCE pin can be driven by TTL level or CMOS level.
NTC (pin 6): battery temperature detection input. Connect the pin to the output of the NTC sensor of the battery. If the voltage of the NTC pin is small
At 180mV or more than 1.35V, it means that the battery temperature is too high or too low, and the charging is suspended. If the NTC is suspended, the battery temperature detection function is canceled and other charging functions are normal.
BAT (pin 7): battery voltage detection terminal. When charging stops, the leakage current of BAT pin is less than 3uA.
VS (pin 8): battery current detection terminal. A high-precision milliohm resistor RS is connected between this terminal and BAT to set the charging current during fast charging,
The formula is: IBAT= 0.0667/RS.
GND (pin 9): Power supply ground. The GND end must be reliably connected to the bottom cooling fin of the chip and the PCB board with copper.
LX (pin 10): connection point of built-in power MOSFETs. The current output terminal with LX of CXLB73278 is connected to the external inductor as the battery charging current.
The input terminal.
IV. Workflow and protection mechanism
4.1. Charging process:
· Stream elimination charging: When the battery voltage is lower than 2.85V, it is precharged with a small current of about 200mA.
· Constant current fast charge: enter the set current fast charging mode after the battery voltage rises
· Constant voltage charging: When the battery voltage approaches 4.2V, the current gradually decreases.
· Charging termination: stop charging when the current drops to the set threshold (such as 200mA), NSTDBY output low level
4.2. Comprehensive protection functions:
· Input adaptation: When the input voltage is as low as 4.55V, the current will be automatically reduced to protect the adapter.
· Overvoltage/undervoltage lockout: VIN overvoltage threshold is 6.3V, undervoltage threshold is 3.95V
· Over-temperature protection: automatically reduces flow when the junction temperature exceeds 145 ℃ to prevent overheating damage
· Output short circuit protection: input current limiting mode when the output voltage is lower than 2.2V
· Automatic recharge: restart charging after the battery voltage drops by 150mV
V. PCB layout and heat dissipation suggestions
CXLB73278 adopts DFN3x3-10L small package, and the heat dissipation mainly depends on PCB design:
·Design 1.7 × 3.0mm heat dissipation pad at the bottom of the chip
·Arrange multiple 0.8mm aperture heat dissipation vias to connect to the inner layer or back Copper cover
·Tin is poured from the back during welding to ensure smooth heat access between the chip and PCB.
·Expand the surrounding area by copper foil as much as possible to improve the heat dissipation effect
·Avoid arranging other heat sources around the chip to prevent mutual influence
6. Typical application scenarios
CXLB73278 is widely applicable:
·Digital camera, video camera
·Electronic cigarette equipment
·Electric toys, small tools
·MP3/MP4 player and other portable audio devices
·White LED driver (3w ~ 11W)
Its high integration and comprehensive protection mechanism make it an ideal efficient charging solution in 5V adapter environment.
VII. Extended application design
CXLB73278 can also be used to drive white LED arrays. Because its output voltage is limited to 4.2V, it can provide stable driving current for a single or multiple parallel WLED, and the driving power covers 3W to 11W, which is suitable for backlight or lighting systems.
VIII. Schematic diagram of typical application circuits
Nine,Summary
As a high-efficiency lithium battery charging management chip specially designed for 5V adapter environment, CXLB73278 has become the preferred power supply solution for all kinds of portable devices with its high precision, high efficiency and comprehensive protection function. Its small package and less peripheral design greatly reduce the system complexity and cost, and is suitable for applications that require strict space and reliability.
If you need to obtain CXLB73278 samples, technical materials or apply for support, please visitJTM-IC official websiteQuery details.
10. Download the relevant chip selection guide -More similar products....
