Hi Champs,
My customer is using MSP430G2433 in their products. When they were taking voltage drop test, they found the behavior of MCU was abnormal. The AC input voltage(220VAC) would disappear for 1.5s, then 3.3V and 5V will be power down, then power up again.
MSP430G2433 with 12MHz(2.5V Vcc at least) MCLK, SPI master was used. ACLK, MCLK, SMCLK were driven by internal clock source. When taking voltage drop test, +3.3V would drop to 1.1V~1.4V with 533ms, then repower up again. From chapter 5.11(BOR/POR) of datasheet, we can know V(B_IT–) =1.35V, which is very close to the lowest Vcc level. We have several questions as follows:
1. From the scope capture we can know RST would be pulled down when Vcc was 2.5V. From datasheet V(B_IT–) =1.35V, looks this value cannot follow the datasheet. Can you help to check this?
2. What would be happened, when MCU was set to 12MHz with lower power supply, which is less than 2.5V?
3. When re-power up again, the lowest voltage level of RST is about 520mV, not zero. Is there any internal resistor on RST internally?
4. The duration time of RST after power up is about 160ms, and from datasheet, td(BOR) is about 2ms. Why this condition happened?
Thanks a lot.
Regards,
Young