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ETA9697 is an ultra low power PMU with 2 channels: a 16/ single cell Libattery linear charger and a 5V Boost synchronous converter with trueshutoff function. The linear charger fully integrated constant Current((O)/Istant voltage(CV)control module and charge FE, With minimalextemal devices. It also has pre-charge funct on for trickle charging deeplydischarged battery and its fast charge current can be programmed by anexternal resistor. When (V Charge stage is entered, charge will beterminated once the charge current drops to 1/10 of the programmed valueA"STAT"pin is also available to indicate the charge status. And the lowpower 5V Boost converters apable of delivering 0.4A current at 5V output.It can be shut down by puling ENBST low, it disconnect the output fromthe BAI to further decrease the system standby power. Its 1. 4MHZswitching frequenc enable a very small external inductor with inductanceas low as 2.2UH The ETA9697, asa whole, is an ideal for the system solutionthat requires very low standby power and compact PCB board size
FEATURESe Ultra low When standby, Ibat<SUA16vinput standoff voltagee 4 2V Charge termination voltageCharge current programmable, up to 1. 2AOutput Disconnect and SCP at 5voutput?5V0.4 Output PowerUp to 94% Efficiency for Boost converterFunctioning with NO BATTERYLogic Control Shutdown and Thermal shutdownESOP8 PackageAPPLICATIONSTWS BT earbuds charge caseBluetooth applicationBattery powered LOT module◆ Power Bank
TWS 耳机充电盒里面的电源pcba主要有两大用途，既要负责充电盒内部电池充电，还需要负责充电盒内部电池升压输出为耳机充电。此外还肩负安全防护，防止内置锂电池过充、过放、短路、过流等保护功能。首先，控制外部电源给TWS耳机电池盒充电，将外部充电器电量充入锂离子电池。这里的外部充电器主要为5V的充电器，如常见的手机适配器，接口为MicroUSB或USB-C，然后降压转化为锂离子电池所需的4.2V电压进行充电，此外还有4.3V或4.35V多个规格。充电芯片有分为线性和开关两种，其中开关充电效率高、发热低，是目前主流的充电方式。
其次，TWS耳机电池盒电源PCBA还需要对外给TWS蓝牙耳机供电，这时又会将锂离子电池升压为5V，然后输出给耳机，耳机通过内部的充电电路完成对内置电池的充电。如此一来，当TWS耳机需要用电的时候，就可以放回充电盒自动补充电量。
充电盒升压芯片也分为同步和非同步两种，其中同步架构的效率高、发热低，非同步整流效率低一些，和移动电源的道理是一样的
原文地址：https://blog.51cto.com/13121602/2373304