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BQ25703A工作在Boost Mode,电感和MOS发热量大

Other Parts Discussed in Thread: BQ25703A, BQSTUDIO

Hi TI,

我目前是采用12V输入适配器给4S1P的LiFePo4电池(最大14.6V)充电,充电芯片BQ25703A工作在Boost Mode,bqstudio上位机寄存器配置如下:

Charge Option 0 820E
Charge Current Register 0800
Charge Voltage Register 3900
OTG Voltage Register 0000
OTG Current Register 0000
Input Voltage Register 2100
Minimum System Voltage 2D00
Input Current Register 3C00
Charge Status Register B400
Prochot Status Register 0040
Input Current Limit In Use 3C00
VBUS and PSYS Voltage Read Back 8410
Charge and Discharge Current Read Back 1E00
Input Current and CMPIN Voltage Read Back 3900
System and Battery Voltage Read Back B2B1
Manufacture ID and Device ID Read Back 7840
Device ID Read Back 1078
Charge Option 1 9210
Charge Option 2 02B7
Charge Option 3 0000
Prochot Option 0 4A54
Prochot Option 1 8128
ADC Option 2000

上述配置

VIN=12V,VBUS=12V,VSYS&VBAT(电压慢慢上升至14.52V),充电电流是2024mA,会发现充电过程Boost中的电感(L1)和两个MOS管(Q14&Q16)以及BQ25703A芯片发热量大,充电电流配置越大越烫,充电电流改成1024mA就没什么问题。

NMOS管选的是NTMFS4833NT3G,RDS(ON)= 2.0mR@10V,Id(max)=191A,SO-8 FL封装;

电感:74437356022    2.2 μH, 8.5 A, 0.0203ohm;

下图六张是SCH、PCB、信号波形和热图,

请问上述发热现像正常吗?关键的几个信号波形对比如何?PCB布局(需要加大散热面积)有什么建议吗?