Hello,
We made about 80 boards, using the LM3880 to control the power-on sequence. All boards work properly at room temperature（25°C）. But at -40 ° C, 3 out of these boards cannot be powered up. We find that the LM3880 on these three boards cannot work properly at -40°C.
The circuit of the LM3880 is as follows. The input power of the board is VCC_5V.
We did some tests on these LM3880s at -40°C. The phenomenon is as follows：
1. Three FLAG output pins of these LM3880s hold low at -40°C. The voltage at the EN pin is 2.4V.
2. I measured the time it takes for the board's power supply to rise from 0V to 5V to be about 20ms.
3. I changed the value of capacitor at the EN pin (C630) to 220nF. The abnormal board still cannot be powered up at -40°C.
4. I changed the value of capacitor at the EN pin (C630) to 1uF. The abnormal board still cannot be powered up at -40°C.
5. I replaced the capacitor at the EN pin with two voltage divider resistors. The circuit is shown as follows：
It still not work，The abnormal board still cannot be powered up at -40°C.
6. I moved the LM3880 on the normal board to the abnormal board. The abnormal board becomes can be powered up at -40°C. It looks like some LM3880s are defective at -40°C.
7. I add a switch on the power cable of the board. Make the power supply rise from 0V to 5V immediately. The abnormal board becomes can be powered up at -40°C.
What is the reason why some LM3880 chips work abnormally at -40 °C? Is there any problem of my circuit?
