本帖最后由 hujianmingeddy 于 2011-4-29 18:07 编辑
8 充放电IC芯片放大效果图: 其原因PDF为:ACDET: AC or adapter power detection. This input pin is used to determine the presence of the ac adapter. When the voltage level on the ACDET pin is less than VACPRES, the bq24702/bq24703 is in sleep mode, the PWM control is disabled, the BATDRV is driven low, and the ACDRV is driven high. This feature can be used to automatically select battery as the system power source. ACDRV: AC or adapter power source select output. This pin drives an external P-channel MOSFET used to switch to the ac wall-adapter as the system power source. When the ACSEL pin is high while the voltage on the ACDET pin is greater than VACPRES, the output ACDRV pin is driven low (VHSP). This pin is driven high (VCC) when the ACDET is less than VACPRES. ACPRES: This open-drain output pin is used to indicate the presence of ac power. A logic high indicates there is a valid ac input. A low indicates the loss of ac power. ACPRES is high when the voltage level on the ACDET pin is greater than VACPRES. 简单翻译后的中文为: ACDET: AC 或适配器电源检测。 这个输入引脚用于确定AC 适配器。
当上ACDET引脚的电压水平比VACPRES少,bq24702/bq24703是在睡眠模式下,PWM 控制被禁用,BATDRV驱动低,ACDRV驱动高。此功能可用于
自动选择电池作为系统电源。 ACDRV:交流适配器电源选择输出。该引脚驱动外部P沟道 MOSFET使用
切换到交流电源适配器作为系统的电源。当 ACSEL引脚为高,而对电压
ACDET销大于VACPRES, 输出ACDRV引脚置低 (VHSP) 。该引脚驱动为高电平(VCC), 当ACDET小于VACPRES。 (经过软件大概翻译) 9通过两个比较器来实现,适配器的选择。 在U7-A模块里,第3脚电压为3个电阻分压而来,第2脚为比较电压 2VREF。 通过计算可知U7第3脚电压为:Upin3=19*(R528+R526)/(R530+R528+R526)=3.5V。 比较输出由3.5V经过R525上拉的ADP_PRES_即第一脚。在ACDET脚电压为经过R609电压下降到3.1V左右。然而ACPRES脚确是由+V3AL上拉的 3.3V。 所以 ACDRV#输出 8V左右电压导通 Q13。此时BATDRV#电压为 18V保持 P管截止状态。 到此为止这板的隔离保护充放电路思路清晰多了。 续下。。。。。。。。。。。。。 |