TLV320AIC3268 control signal current backflow problem

杨俊

TLV320AIC3268 control signal current backflow problem [Copy link]

Dear experts, I now have the following problem:

1. The hardware uses STM32's SPI to configure AIC3268, but 3268 does not work properly at a low temperature of around -15°C (other temperatures are normal).

2. Disconnect the 3.3V power supply of AIC3268 at room temperature, and STM32 works normally. It is found that there is a serious backflow phenomenon. A voltage of 2.4V can be measured on the 3.3V pin of 3268. Therefore, 3268 can work normally without 3.3V power supply.

3. Supply 3.3V power to 3268 externally, and power on 3268 first, and then power on STM32. It still cannot work normally at a low temperature of -15℃.

4. Based on the second step, set the IO port of STM32 from push-pull to OC output to drive 3268, and then test the reverse voltage on the 3.3V pin of 3268 to be 0.6V, and the low temperature of -15℃ is also normal.

Regarding the above phenomenon, I would like to ask a few questions:

1. What is the input composition of the 3268 internal control interface? Why is backflow so serious?

2. Power on 3268 separately first, which can theoretically avoid backflow, but the low temperature of -15℃ is still abnormal. Why can't I figure it out?

Please answer this question, thank you!

Jacktang

At low temperatures of around -15°C, 3268 does not work properly. Analyzing the original poster's problem, if the current from the input to the power supply exceeds the clamping current, the AIC3268 may fail.

Jacktang

If the 3268 is powered by 3.3V externally, and the 3268 is powered on first, and then the STM32 is powered, it will still not work properly at a low temperature of -15℃.

In this case, it should be VCC power supply. If you disconnect the peripheral circuit, see if it works.

tagetage

I think it is a problem with hardware circuit design or PCB welding.

chunyang

"Backflow" does not exist, but is caused by the input clamp protection diode of the COMS circuit. As long as there is a high level with sufficient driving capability on any IO, when Vcc is not powered, the IO port clamp diode provides a path for the external high level to connect to Vcc. Due to the existence of tube voltage drop, the "backflow" voltage at this time will be one tube voltage drop lower than the external high level.

chunyang

At low temperatures, some device parameters may exceed the range of the designed timing error. The solution is to pay attention to the control interface timing. Abnormal leakage must be avoided, of course. The IO mode of the MCU must be properly configured after power-on. If the power-on reset timing of the peripheral chip cannot match the MCU, the MCU needs to actively control the power-on reset, or use an external reset circuit to make the reset time of the peripheral chip longer than the MCU, that is, to ensure that the external chip completes the power-on reset after the MCU enters the normal working state. Of course, at this time, the MCU is required to ensure that the peripheral chip has entered the normal working state before issuing instructions to operate the peripheral chip.