CXLB73277 is a synchronous step-down lithium ion battery charging management chip based on a fixed switching frequency of 1.5MHz. The input voltage range is 3.8V to 6.5V, supporting a maximum of 2A continuous charging current. It adopts high-efficiency synchronous buck topology, with charging efficiency exceeding 90% and low calorific value, effectively improving system reliability.
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[ CXLB73277 ]"
CXLB73277: high efficiency 2A Li-ion battery charger with 1.5MHz synchronous step-down and multiple intelligent protection
With the increasing popularity of mobile phones, tablet computers, digital cameras and other portable devices, high-performance, small size and high safety battery charging management chips have become the core of the design. As an efficient 2A CXLB73277 designed for 5V adapter environment, Li-ion battery charger relies on its 1.5MHz high frequency synchronous step-down Architecture, comprehensive protection mechanism and flexible configuration capability, it has become an ideal power solution for all kinds of portable devices. This paper will deeply analyze its technical characteristics, working principle and design points, and help engineers to realize a more compact and efficient charging system.
I. Product Overview
CXLB73277 is a synchronous step-down lithium ion battery charging management chip based on a fixed switching frequency of 1.5MHz. The input voltage range is 3.8V to 6.5V, supporting a maximum of 2A continuous charging current. It adopts high-efficiency synchronous buck topology, with charging efficiency exceeding 90% and low calorific value, effectively improving system reliability.
The chip integrates a complete charging management process, including three-stage charging of current elimination, constant current and constant voltage, with a charging voltage accuracy of ± 1%, meeting the precise charging requirements of lithium ion/lithium polymer batteries. It is packaged in ESOP8 or MSOP8 with cooling fin, and the peripheral components are simple and suitable for space-sensitive applications.
II. Core features
· Input voltage range: 3.8V to 6.5V
· Synchronous step-down Architecture: 1.5MHz fixed frequency, efficiency> 90%
· Maximum 2A charging current, external resistance adjustable
· High precision float-charge pressure: 4.2V ± 1%
· Two-way open and leak status indication(NCHRG/NSTDBY)
· Battery temperature monitoring, supports NTC thermistor
· Soft start, short circuit protection, automatic recharge
· Low Standby current: 140% A
· C/10 charging termination mechanism, effectively protect battery life
3. Pin functions and design points
3.1. Pin definition:
· VCC: power input, support 3.8V to 6.5V
· NCHRG/NSTDBY: Charging/full status indication
· TS: enable control and temperature detection multiplexing pin
· BAT: battery connection terminal, providing charging current and voltage
·: output current detection positive input
· LX: switch node, connecting external inductance
· GND: System, reliable connection with heat dissipation pad
3.2. Charging current setting:
The charging current is set by the detection resistor RS connected between VS and BAT, and its relationship is as follows:
For example, if the charging current is set to 1A, the RS value is 0.1 Ω; If the charging current is set to 2A, the RS value is 0.05 Ω. Users can select the appropriate resistance value according to actual needs.
3.2. Temperature monitoring and enabling control:
TS pin has both enable and temperature detection functions:
·Connect to VCC: disable temperature detection
·Connect to GND: enter standby mode and stop charging
·Connect to NTC network: enable temperature protection, voltage range: 45% to 80%× VCC
IV. Workflow and protection mechanism
4.1. Charging process:
Discharge charging: when VBAT is less than 2.9V, it is precharged with a small current of about 200mA.
Constant current charging: enter the set current fast charge after the battery voltage rises
Constant voltage charging: when VBAT approaches 4.2V, the current gradually decreases.
Charging termination: stop when current drops to C/10, NSTDBY output low level
4.2. Comprehensive protection functions:
·Undervoltage/overvoltage locking: VCC undervoltage threshold is 3.7V
·Over-temperature protection: automatic flow drop when junction temperature exceeds 145 ℃
·Short circuit protection: input current limiting mode when the output voltage is lower than 1.2V
·Automatic recharge: restart charging when VBAT drops to 4.05V
·Input adaptation: prevent adapter overload
V. PCB layout and heat dissipation design
CXLB73277 adopts ESOP8 package, and the heat dissipation performance depends on PCB design:
·Design 2.5 × 6.5mm heat dissipation pad at the bottom of the chip
·Four heat dissipation vias with 1.2mm aperture and 1.6mm spacing are arranged.
·Tin is poured from the back during welding to ensure smooth heat dissipation path between chip and PCB.
·Expand the surrounding area of copper foil to improve the heat dissipation effect
·Avoid arranging other heat sources around the chip
6. Typical application scenarios
6.1. CXLB73277 is widely applicable:
·Mobile phones and smart phones
·Tablet PC, portable stereo
·MP3/MP4 player
·Digital camera, video camera
·GPS navigation equipment, electronic dictionary
·White LED driver (0.5W ~ 7W)
6.2. Its high integration and small encapsulation make it an ideal battery management solution for all kinds of portable devices.
VII. Extended application: White LED driver
CXLB73277 can also be used to drive white LED arrays. Under the condition of 6V input, it can provide stable driving current for single or multiple WLEDs in parallel. The output current is set by RS, and the driving power covers 0.5W to 7W, which is suitable for backlight or lighting systems.
VIII. Schematic diagram of typical application circuits
IX. Summary
CXLB73277, as a high-efficiency lithium battery charging management chip facing the 5V adapter environment, has become the preferred solution for power supply design of portable devices by virtue of its 1.5MHz high-frequency operation, high-precision voltage control and comprehensive protection functions. Its simple peripheral circuit and good heat dissipation performance further reduce the complexity and cost of the system, and is suitable for applications with strict requirements on volume and reliability.
If you need to obtain CXLB73277 samples, technical materials or apply for design support, please visitJTM-IC official websiteLearn more.
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