AN3326 Datasheet, PDF (19/21 Pages) STMicroelectronics – SPC56EL60x hardware design guideline

AN3326
6
Reference reset circuit
Reference reset circuit
The SPC56EL60x external reset pin is a bidirectional low active signal.
For safety reasons an internal weak pull down structure is implemented. In such a
configuration, if the reset pin is open (for example, due to a faulty condition), the device is
remains in reset state.
This pin acts as an input to initialize the SPC56EL60x to a known start-up state and acts as
an output when an internal device function causes a reset.
The minimum reset pulse duration is 500 ns.
Figure 13 shows the suggested reset circuit. Basic components are:
 External open-drain microprocessor reset device
 External pull-up resistor (R_P)
 NOR gate digital port to manage multiple reset sources
Figure 13. Reference reset circuit
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The value of the pull-up resistor must be chosen according to the internal pull-down resistor
integrated in SPC56EL60x and the external reset device component. For example, using
the STM6315RDW13F as microprocessor reset, a resistor of 2.2Kworks properly.
DocID18333 Rev 3
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