58.4 External Reset Circuit

The external Reset circuit is connected to the RESET pin when the external Reset function is used. The circuit is not necessary when the RESET pin is not driven low externally by the application circuitry.

The reset switch can also be removed, if a manual reset is not desired.

A pull-up resistor makes sure that the reset does not go low and unintentionally causing a device reset. An additional resistor has been added in series with the switch to safely discharge the filtering capacitor, that is preventing a current surge when shorting the filtering capacitor which again can cause a noise spike that can have a negative effect on the system.

Place the components illustrated within one-half inch (12 mm) from the RESET pin.

Figure 58-7. External Reset Circuit Schematic
Note: These values are only given as a typical example. Refer to the Power Supply Electrical Specifications to determine the proper values given in the system parameters to meet the reset timing requirements (TRST).
Note: Reset circuit recommendations to improve EFT/ESD/EMI immunity can be found in the “Basic 32-Bit MCU Design and Troubleshooting Checklist Guide” on the Microchip web site.