Shenzhen Mingjiada Electronics Co., Ltd. supplies the TI BQ24250, a highly integrated single-cell lithium-ion battery charger with power path management functionality.
The BQ24250 is a highly integrated single-cell lithium-ion/lithium-polymer switch-mode charger launched by Texas Instruments (TI), designed specifically for portable, miniaturised electronic devices. The chip integrates a synchronous buck charging architecture, an intelligent power path management system, multi-stage charging control and a comprehensive set of safety protection circuits. It enables safe and efficient charging of single-cell lithium batteries and system power supply switching without the need for additional complex peripheral circuits. It is perfectly suited to portable devices with limited space and high requirements for power supply stability, making it the mainstream charging management solution for consumer portable electronic products.
I. Core Positioning and Fundamental Advantages of the BQ24250
The BQ24250 is part of the BQ2425x series of dedicated charge management ICs. Featuring a single-input power supply design, it is compatible with various standard power inputs, including USB ports and AC mains adaptors, and supports a maximum charging current of 2A, balancing charging efficiency with power consumption control. Compared to traditional discrete charging solutions, the chip’s key advantage lies in its high level of integration and independent power path management architecture, which completely resolves the pain point of traditional chargers where ‘the battery takes priority over the system load’. At the same time, it simplifies PCB layout, reduces hardware development costs and lowers the power consumption of the finished device.
The BQ24250 operates at a fixed switching frequency of 1.5 MHz and can be paired with ultra-thin 1.2 mm inductors, meeting the structural design requirements of slim and lightweight portable devices. It supports an independent I²C communication interface, enabling programmable configuration of charging parameters and real-time reporting of operating status, thereby satisfying the precise power management requirements of smart devices. It also supports a standalone operating mode, allowing basic operation without the need for a host controller, making it suitable for a wide range of simple and smart device applications.
II. Key Hardware Functions and Core Parameters of the BQ24250
2.1 Flexible Input Current Range Configuration
The BQ24250 supports switching between multiple input current limit ranges. Through hardware configuration or I²C programming, it can be set to 100mA, 500mA, 900mA, 1.5A and 2A. It is fully compatible with power inputs of varying capacities, such as USB 2.0, USB 3.0 and standard adaptors, and automatically adapts to the power source’s output to prevent input overload and supply instability. It also supports low-power adaptors, thereby reducing the cost of device accessories.
2.2 High-Efficiency Synchronous Buck Charging Architecture
The chip employs a synchronous switching buck charging topology. Compared to linear charging solutions, this significantly reduces heat dissipation during charging and substantially improves conversion efficiency when converting high-voltage input to low-voltage charging. This effectively minimises the device’s temperature rise and enhances overall system stability. The charging voltage precisely conforms to the standard for single-cell lithium-ion batteries, with high voltage regulation accuracy, effectively preventing overcharging and undercharging whilst ensuring the battery’s cycle life.
2.3 Ultra-Low Power Consumption Operation
The chip incorporates a low-power sleep mode; when the device is not charging or under no load, it automatically enters a low-power standby state. With extremely low static power consumption, it effectively reduces battery self-discharge during periods of inactivity, thereby extending the device’s standby battery life. This makes it suitable for low-power, long-standby devices such as wearable devices and portable testing instruments.
III. Core Function of the BQ24250: Intelligent Power Path Management (NVDC Architecture)
Power path management is the BQ24250’s most distinctive feature. Utilising a Narrow Voltage DC Control (NVDC) architecture and incorporating a Dynamic Power Path Management (DPPM) circuit, it intelligently switches power supply paths to achieve dynamic power allocation amongst the input power supply, battery and system load, thereby thoroughly optimising the power supply logic of portable devices.
3.1 Instant Power-On Function in Battery-Less or Deeply Discharged Conditions
Traditional charging chips are unable to supply power to the system load when the battery is deeply discharged or absent, preventing the device from starting up. In contrast, the BQ24250’s power path architecture enables instant start-up even in the absence of a battery or when the battery is deeply discharged. Upon connection to an external power source, the input power directly supplies the system load without the need for the battery, significantly enhancing the device’s operational flexibility and making it suitable for scenarios such as device debugging, emergency use and battery replacement.
3.2 Dynamic Power Allocation and Battery Recharging
The chip incorporates built-in real-time current and voltage monitoring circuits that continuously monitor the output capacity of the input power supply and the power consumption of the system load. When the instantaneous peak load exceeds the supply capacity of the input power supply, the power path management system automatically triggers battery recharging mode, whereby the battery works in conjunction with the input power supply to power the system. This ensures stable operation of the device at full load and prevents issues such as device reboots or crashes caused by instantaneous power consumption peaks.
Conversely, when the input power supply is sufficient, the system prioritises power from the external source, with any surplus power being used entirely for battery charging. This enables simultaneous power supply and charging, maximising the utilisation of input power and enhancing both charging and power supply efficiency. At the same time, this mechanism allows the device to be paired with a lower-wattage adapter, reducing the overall size and cost of the device’s components.
3.3 System Voltage Stabilisation Protection
The chip monitors the system output voltage (SYS pin) in real time. Should a sudden change in load cause the system voltage to drop to the minimum threshold (VMINSYS), the DPPM circuit automatically reduces the charging current to prioritise the system’s power supply, stabilising the operating voltage and preventing voltage fluctuations from affecting the operation of precision components such as the device’s main controller and sensors, thereby significantly enhancing operational stability.
IV. BQ24250 Four-Stage Standard Lithium-Ion Battery Charging Process
The BQ24250 strictly adheres to the standard charging logic for single-cell lithium-ion batteries, comprising four stages: trickle charging, pre-charging, constant-current fast charging and constant-voltage termination. With intelligent control throughout the entire process, it accommodates batteries in various states—including new, deeply discharged and aged cells—striking a balance between charging speed and battery safety.
4.1 Trickle Charging Stage
For batteries with extremely low voltage or those that have been deeply discharged, the chip initiates low-current trickle charging to gradually reactivate the battery cells and restore the active material in discharged batteries. This prevents issues such as overheating, swelling and damage caused by direct high-current charging, thereby laying a safe foundation for subsequent fast charging.
4.2 Pre-charging Stage
Once the battery voltage has recovered to the threshold, the pre-charging stage begins. The charging current is gradually increased to stabilise the battery’s voltage and internal resistance, eliminate cell voltage fluctuations, prevent abnormal currents during the constant-current fast-charging stage, and ensure a smooth transition throughout the charging process.
4.3 Constant-Current Fast-Charging Phase
Once the battery voltage reaches the normal range, the system enters the high-current constant-current charging phase. Energy is continuously supplied at the set maximum charging current to rapidly increase the battery’s charge level, significantly reducing the overall charging time and meeting the fast-charging requirements of high-capacity lithium-ion batteries.
4.4 Constant-Voltage Termination Phase
When the battery voltage approaches the full-charge threshold, the system switches to constant-voltage charging mode. The charging current gradually decreases as the battery reaches saturation; when the current drops to the termination threshold, charging stops automatically, completely eliminating the risk of overcharging, precisely completing the charging closed-loop and protecting the battery’s cycle life.
V. BQ24250 Comprehensive Safety Protection Mechanism
The BQ24250 incorporates a complete set of hardware-level safety protection circuits, eliminating the need for external auxiliary protection components. It comprehensively mitigates various risks during charging and power supply processes, enhancing the safety of both the device and the battery, and meeting safety certification standards for portable devices. Key protection functions include:
- Overvoltage protection: Triple protection against input overvoltage, battery overvoltage and system output overvoltage; power supply and charging circuits are immediately disconnected if limits are exceeded;
- Overcurrent protection: Input current limiting, charging overcurrent and load short-circuit overcurrent protection to prevent abnormal currents from damaging the chip and peripheral components;
- Over-temperature protection: Built-in temperature monitoring automatically reduces power or stops charging when the chip junction temperature exceeds limits, and automatically resumes operation once the temperature has dropped;
- Short-circuit protection: Instantaneous power cut-off protection against short circuits in the system load or battery port, eliminating the risk of fire or component damage caused by short circuits;
- Charging timeout protection: Timeout detection mechanisms are in place for each charging stage to prevent prolonged overcharging or ‘phantom charging’ caused by the battery becoming stuck in an abnormal state.
VI. Main Application Scenarios for the BQ24250
Thanks to its core advantages of high integration, compact size, high stability and intelligent power management, the BQ24250 is widely used in various slim and portable electronic products powered by single-cell lithium batteries. Typical applications include: smart wearable devices (fitness trackers, smartwatches), portable testers, wireless Bluetooth earphone charging cases, small smart home devices, handheld consumer electronics and portable medical devices. It is the chip of choice for charging management in compact, highly stable portable devices.
VII. Summary of the BQ24250
As a high-performance single-cell lithium-ion battery charge management IC, the TI BQ24250 features NVDC intelligent power path management as its key highlight, addressing industry pain points associated with traditional charging solutions, such as conflicts between power supply and charging, poor load stability, and the inability to power on without a battery. Furthermore, leveraging advantages such as highly integrated hardware design, four-stage precision charging logic, comprehensive safety protection and programmable parameter configuration, it balances ease of development, device stability and battery lifespan. It is perfectly suited to the power supply and charging requirements of various lightweight, intelligent portable electronic devices, offering exceptional value for engineering applications.
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