DocID024134 Rev 2

5/17

AN4232

Overview of analog comparators

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Overview of analog comparators

1.1

Hysteresis

A comparator compares the inverting input with the non-inverting input and even small

voltage fluctuations cause bounce on comparator the output. This bounce is not acceptable

in many applications. Figure 1 shows the output bouncing when the input is noisy.

Figure 1. Effect of a noisy input on a comparator output

This bounce on the comparator output can be prevented by adding hysteresis into

comparators. The analog comparators in STM32F37x and STM32F30x devices have a

configurable hysteresis value: no, low, medium and high hysteresis value. Table 2 shows

the typical values of an hysteresis in each configuration.

Caution:

The hysteresis feature is not available on the following microcontrollers:

STM32F301x6/8, STM32F302x6/8, STM32F303x4/6/8, STM32F334xx, STM32F302xD/E

and STM32F303xD/E.