Is there something wrong with the application of this Zener diode?

elec32156

Is there something wrong with the application of this Zener diode? [Copy link]

This is the input port protection of 3.7V battery equipment. The maximum voltage of the battery is 4.2V. After entering, a conventional TVS tube TVS1 is connected, which can be used for surge protection and ESD protection;

A Zener diode is added at the back end. The voltage regulation range of the Zener diode is 4.98V~5.2V. The parameters are shown in the figure below. This application is a circuit commonly used in mobile phone solutions in the early years.

I would like to ask, is the application of this Zener diode unreasonable here? It is different from the conventional application and does not work in a voltage-stabilized state. However, the manufacturer's reference design does add it. What is the main consideration?

qwqwqw2088

The voltage range of the Zener diode selected here is 4.98V~5.2V, and the connection to the charger should be taken into consideration.

吾妻思萌

Prevent reverse connection or abnormal surge?

vincentc543

This is for overvoltage protection, a mechanism to protect the battery.

vincentc543

This is an overvoltage protection mechanism to protect the battery by limiting the voltage to below 5V to prevent the battery from being damaged.

chunyang

If there is no external power supply, then there is no need to use it.

elec32156

vincentc543 posted on 2022-8-8 09:00 This is for overvoltage protection, a mechanism to protect the battery, limiting the voltage to below 5V to prevent the battery from being damaged...

Under what circumstances can such a voltage be generated on the link and flow back to the battery? The Vbat link connects the input of the PMU and the output of the charger, and the actual input voltage of the PMU (model MT6328) is only 4.5V, and the limit value is 5V. It cannot withstand a voltage higher than 5V. Therefore, if such a high voltage exists on the link, the priority will be to protect the PMU instead of the battery.

tomas_li

Why don't you have a current limiting resistor in series with your Zener diode? The maximum reverse voltage of your Zener diode is only 2uA. If the current is not limited, it will easily exceed 2uA.