Figure 8. Nrst Circuitry Timings Example (Not To Scale, Only For Stm32F411Xx And Stm32F446Xx) - ST STM32F4 Series Getting Started

AN4488
Selection of NRST voltage supervisor
Voltage supervisor should have the following characteristics
•
Reset output active-low open-drain (output driving low when voltage is below trip
point).
•
Supervisor trip point including tolerances and hysteresis should fit the expected V
range.
Notice that supervisor spec usually specify trip point for falling supply, so hysteresis
should be added to check the power on phase.
Example for STM1061N16:
–
–
Figure 8. NRST circuitry timings example
(not to scale, only for STM32F411xx and STM32F446xx)
Voltage regulator 1.8 V +/- 5% mean V
Supervisor specified at 1.60 V +/- 2% with an hysteresis of 5% mean
- rising trip max = 1.71 V (1.60 V + 2% + 5%)
- falling trip min = 1.57 V (1.60 V - 2%).
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min1.71 V
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