Figure 6. Pdr_On Timings Example - ST STM32F4 Series Getting Started

AN4488
Selection of PDR_ON voltage supervisor
Voltage supervisor should have the following characteristics
•
Reset output active-high push-pull (output driving high 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:
–
–

Figure 6. PDR_ON timings example

(not to scale, not needed for STM32F411xx and STM32F446xx)
Voltage regulator 1.8V +/- 5% mean V
Supervisor specified at 1.66V +/- 2.5% with an hysteresis of 0.5% mean
- rising trip max = 1.71V (1.66V + 2.5% + 0.5%)
- falling trip min = 1.62V (1.66V - 2.5%).
DocID026304 Rev 3
min1.71V
DD
Power supplies
DD
13/44
43