单片机VCC输入3.3V 不工作 求解

你确定VBB小于2.3V的时候正常工作，如果输出还是3.3V，正常工作的话，你可以检查一下你的熔丝位设置，BOD位，看看掉电检测设置是不是有问题。

我说的正常工作指的是升压芯片

BOD  掉电检测怎么设置呢   我的 BODLEVEL 为1  BODEN 为0

BOD  掉电检测怎么设置呢   我的 BODLEVEL 为1  BODEN 为0

我帮你看了一下ATmega8的数据手册，你可以看附件我的截图，加上下面的描述，里面讲到你设置BODLEVEL=1的话，在2.4V左右会掉电，进入reset，所以你想提高工作电压就把BODLEVEL设为0，BODEN是使能位，0表示开启。
1. The Power-on Reset will not work unless the supply voltage has been below VPOT (falling)
2. VBOT may be below nominal minimum operating voltage for some devices. For devices where
this is the case, the device is tested down to VCC = VBOT during the production test. This guarantees
that a Brown-out Reset will occur before VCC drops to a voltage where correct
operation of the microcontroller is no longer guaranteed. The test is performed using BODLEVEL
= 1 for ATmega8L and BODLEVEL = 0 for ATmega8. BODLEVEL = 1 is not applicable
for ATmega8