TI公司的BQ25798是I2C兼容一节到四节电池5A降压/升压电池充电器,具有双输入选择器,太阳能板MPPT和快速备份模式. BQ25798是全集成的开关模式降压-升压充电器,用于1-4节锂电池和聚合物锂电池.集成包括4个开关MOSFET,输入和充电电流检测电路,电池FET和所有的降压/升压转换器的回路补偿.它采用NVDC功率通路管理,调整系统不会降落到可配置的最低系统电压.当系统功率超过输入源额定指标时,电池补充模式支持系统不会超过输入源指标.采用内置的VOC缩放MPPT算法BQ25798最大化光伏电池板的最大功率.BQ25798在备份模式支持从适配器到转换器电池电压的超快切换.器件具有大功率密度,支持USB PD 3.0,开关频率750-kHz 或1.5-MHz,5A充电电流,10mA分辨率,96.5%效率,支持广泛的输入源,从电池(USB OTG)的供电USB端口,2.8V-22V OTG输出电压,分辨率10mV,支持USB-PD PPS,OTG输出电流调整高达3.32A,分辨率40mA,器件集成了16位ADC用于电压,电流和温度监测,仅工作时静态电流为17 μA,充电关断模式为500nA.2节电池充电电压调整为-0.25%到+0.65%,充电电流调整为±5%,输入电流调整为 ±5%,29引脚4mmx4mm QFN封装.主要用在可视门铃,智能家庭控制,数据集中器,割草机器人,财产跟踪,移动POS,多参数病人监视器,心电仪(ECG)和超声波智能探针.本文介绍了BQ25798主要特性, 功能框图和简化电路图,多种应用框图,以及评估板BQ25792/8EVM主要特性,电路图,材料清单和PCB设计图.

BQ25798 I2C Controlled, 1- to 4-Cell, 5-A Buck-Boost Battery Charger with Dual-Input
Selector, MPPT for Solar Panels and Fast Backup Mode

The BQ25798 is a fully integrated switch-mode buck-boost charger for 1-4 cell Li-ion batteries and Li-polymer batteries. The integration includes 4 switching MOSFETs, input and charging current sensing circuits, the battery FET and all the loop compensation of the buck-boost converter. It uses NVDC power path management, regulating the system not dropping below a configurable minimum system voltage. When system power exceeds the input source rating, battery supplement mode supports the system without overloading the input source. BQ25798 It also maximizes power from photovoltaic panels using its built-in VOC scaling MPPT algorithm. BQ25798 supports ultra-fast switchover from the adapter to a converted battery voltage in Backup Mode.

The charger supports the narrow VDC power path management, in which the system is regulated at a voltage slightly higher than the battery voltage without being allowed to drop below the minimum system voltage. The minimum system voltage allows the system to operate even when the battery is completely discharged or removed. When system power exceeds the input source rating, battery supplement mode supports the system

power requirement without overloading the input source.

The device charges a battery from a wide range of the input sources including legacy USB adapter to high voltage USB PD adapter and traditional barrel adapter. The charger automatically sets converter to be buck, boost or buck-boost configurations based on input voltage and battery voltage without the host control. The dual input source selector manages the power flowing from two different input sources. The inputs selection is controlled by the host through I2C with default source #1 (VAC1) as the primary input and the source #2 (VAC2) as the secondary input.

To support fast charging using adjustable high voltage adapter, the device provides D+/D- handshake. The device is compliant with USB 2.0 and USB 3.0 power delivery specification with input current and voltage regulation. In addition, the Input Current Optimizer (ICO) allows the detection of maximum power point of an unknown input source. The BQ25798 also provides a Maximum Power Point Tracking (MPPT) algorithm to optimize the power drawn when connected to a solar cell.

Besides the I2C host controlled charging mode, this charger also supports autonomous charging mode. After power up, the charging is enabled with default register settings. The device can complete a charging cycle without any software engagements. It detects battery voltage and charges the battery in different phases: trickle charging, pre-charging, constant current (CC) charging and constant voltage (CV) charging. At the end of the

charging cycle, the charger automatically terminates when the charge current is below a pre-set limit (termination current) in the constant voltage phase. When the full battery falls below the recharge threshold, the charger will automatically start another charging cycle.

In the absence of input sources, this device supports USB On-the-Go (OTG) function, discharging battery to generate an adjustable 2.8-V to 22-V voltage on VBUS with 10-mV step size, which is compliant to the USB PD 3.0 specification defined programmable power supply (PPS) feature. The BQ25798 also provides backup mode to supply a system load at PMID using the adjustable OTG voltage when the adapter is removed.

The charger provides various safety features for battery charging and system operations, including battery temperature negative thermistor monitoring, trickle charge, pre-charge and fast charge timers and over-voltage/overcurrent protections on battery and input. The thermal regulation reduces charge current when the junction temperature exceeds a programmable threshold. The STAT output of the device reports the charging status and

any fault conditions. The PG output indicates if a good power source is present. The INT pin immediately notifies host when fault occurs.

It is available in a 29-pin 4mm × 4mm QFN package.

BQ25798主要特性:

• High power density, high integration buck-boost charger for 1-4 cell batteries supporting any USB PD 3.0 profile

– Integrates four switching MOSFETs, BATFET

– Integrates input and charging current sensing

• Highly efficient

– 750-kHz or 1.5-MHz switching frequencies

– 5-A charging current with 10-mA resolution

• 96.5% efficient: 16-V battery at 3A from 20V

• Supports a wide range of input sources

– Autonomously sampled VOC maximum power point tracking (MPPT) for charging from a photovoltaic panel

– 3.6-V to 24-V wide input operating voltage range with 30-V absolute maximum rating

– Detects USB BC1.2, HVDCP and non-standard adapters

• Dual-input power mux controller (optional)

• Narrow voltage DC (NVDC) power path

• Backup Mode with Ultra-fast switchover to adjustable voltage

• Powers USB port from battery (USB OTG)

– 2.8-V to 22-V OTG output voltage with 10-mV resolution to support USB-PD PPS

– OTG output current regulation up to 3.32 A with 40-mA resolution

• Flexible autonomous and I2C mode for optimal system performance

• Integrated 16-bit ADC for voltage, current, and temperature monitoring

• Low battery quiescent current

– 17 μA for battery only operation

– 500 nA in Charger Shutdown Mode

• High accuracy

– -0.25% to +0.65% charge voltage regulation for 2S batteries

– ±5% charge current regulation

– ±5% input current regulation

• Safety

– Thermal regulation and thermal shutdown

– Input/battery OVP and OCP

– Converter MOSFETs OCP

– Charging safety timer

• Package

– 29-Pin 4 mm × 4 mm QFN

BQ25798应用:

• Video doorbell, Smart home control

• Data concentrators, Robotic lawn mower

• Asset tracking, Mobile POS

• Multiparameter patient monitor, Electrocardiogram (ECG), Ultrasound smart probe

图1. BQ25798简化电路图

图2. BQ25798功能框图

图3. BQ25798应用框图:单输入源和无FET

图4. BQ25798应用框图:双输入源和有FET

图5. BQ25798应用框图:单输入源,备份模式和有FET

评估板BQ25798BKUPEVM (BMS034)

BQ25792EVM, BQ25798EVM and BQ25798BKUPEVM (BMS034) Evaluation Module

The BQ25792 and BQ25798 (BQ25792/8) is an integrated switched-mode buck-boost battery charge management device in QFN package. It is intended to charge 1- to 4-series cell Li-ion and Li-polymer batteries.

The charger features a narrow VDC architecture (NVDC) which allows the system to be regulated to a minimum value even if the battery is completely discharged. Additionally, the BQ25792/8 supports input source detection through D+ and D- which is compatible with USB2.0, USB3.0 power delivery, non-standard adapters, and high voltage adapters. With dual input source selection, USB OTG support, and an integrated 16-bit multi-channel analog-to-digital converter (ADC), the BQ25792/8 is a complete charging solution.

评估板BQ25792/8EVM主要特性:

The BQ25792/8EVM is a complete module for evaluating the BQ25792/8 charger IC in the QFN package. Key features of this EVM include:

• Synchronous Switch Mode Buck-Boost Charger for 1s-4s Battery Configuration for 5-A Charging with 10-mA Resolution

• Support for 3.6-V to 24-V Wide Range of Input Sources USB Auto-Detect, USB PD and Wireless Input

• Dual Input Source Selector to Drive Bi-Directional Blocking NFETs

• Power up USB Port from Battery (USB OTG) with 2.8-V to 22-V OTG Output Voltage with 10-mV Resolution

• Low Battery Quiescent Current < 1 μA in Shutdown Mode

• BQ25798 has MPPT and backup mode features

图6. 评估板BQ25792/8EVM测试电池充电建立图

图7.评估板BQ25792EVM(BMS034A/B-001)和BQ25798EVM(BMS034A/B-003)电路图(1)

图8.评估板BQ25792EVM(BMS034A/B-001)和BQ25798EVM(BMS034A/B-003)电路图(2)

图9.评估板BQ25798BKUPEVM (BMS034A/B-002)电路图

评估板BQ2579XEVM材料清单:

图10.评估板BMS034A/B PCB设计图:顶层

图11.评估板BMS034A/B PCB设计图:信号层1

图12.评估板BMS034A/B PCB设计图:信号层2

图13.评估板BMS034A/B PCB设计图:底层