Post Date : Nov 15, 2023 / Last updated : Dec 08, 2023

Here explains how to select an appropriate detect voltage / release voltage when actually designing a circuit using a voltage detector.

If detect voltage / release voltage is not properly set

Before checking an appropriate selection, let's imagine what happens when you select a wrong detect voltage / release voltage.

As a common case example, there is too high release voltage setting.
In a case example of setting example 1, when

Monitoring Voltage (Output Voltage of LDO) : TYP. 3.300V

Detect Voltage                : TYP. 3.100V

Release Voltage                : TYP. 3.100V x 1.05=3.255V

and the output voltage of LDO decreases, it seems that the voltage drop can be output to MCU without any problem.

However, with an actual electronic device, variability or fluctuation of output voltage or detect / release voltage will be generated in output voltage or voltage detector of LDO depending on manufacturing variations or temperature characteristics, etc.

In a case example of setting example 1, the output voltage of LDO is sometimes lower than the release voltage considering manufacturing variations of IC. In this case, the detector will never return to the release status after entering detection status once.

Setting example 1) When Detect voltage = 3.1V

Setting of an appropriate release voltage / detect voltage

To set a detect / release voltage that does not enter release status for an actual device, it is important to comprehend voltage accuracy (output voltage accuracy of LDO) of monitoring line, detect voltage / release voltage variability of voltage detector, and their temperature fluctuations, etc.

After comprehending these voltage variabilities and fluctuations, it is necessary to set a release voltage so that the lower limit value of voltage of monitoring line becomes higher than the upper limit value of release voltage considering manufacturing variations of IC and temperature fluctuation under actual use conditions, etc. like setting example 2.

Setting example 2) When Detect voltage = 3.0V