Gate resistor choice

AN2986

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Doc ID 15727 Rev 1

Figure 2.

Gate current variation with temperature for Z01 device

1.2

Resistor according to environment accuracy and variation

Temperature is not the only parameter influencing gate resistor choice. Other parameters

have also to be taken into account. Parameters discussed in this section are related to the

accuracy of the components used and to the working environment.

1.2.1

Parameters variations

All the different application parameters that have an impact on gate current level are listed

below.

taken into account. In appliance applications a capacitive power supply is often used. The

main part of this power supply is the Zener diode. Stability of the Zener voltage is the best at

5.1 V and 5.6 V. Accuracy of this power supply is ±10% at 5 V.

Stability of the diode at 3.3 V and 3.9 V is worse and ±0.6 V (±20%) can be achieved. This

result leads to the use of switch mode power supply (SMPS) for a 3.3 V power supply.

Output voltage levels on the I/O pins of the MCU are important variable parameters. The

when tied to ground. This parameter varies with the current flowing through this pin. The

value is given by the MCU datasheet (for example: STM8S10xxx).