GPIO's Push-Pull, Open-Drain concept and application

1. When setting STM32 GPIO, if you look at the MODE, there are Push-Pull and Open-Drain MODE. To find out the difference between the two modes.

2. Push-Pull

1) It is a circuit consisting of two TRs. The upper part is PNP TR (P-MOS), and the lower part is NPN TR (N- MOS).

2) If'Low' is output from Output Control, PNP TR is turned ON and VDD is output to Output.

3) If'High' is output from Output Control, NPN TR is turned ON and VSS is output to the Output.

4) Consist of MOSFET or BJT.

3. Open-Drain & Open-Collector

1) Open-Collector if it is composed of BJT

2) Open-Drain if composed of MOSFET

3) If'High' is output in Output Control, VSS is output to Output.

4) When'Low' is output in Output Control, the output is in Hi-Impedence state.

4. Use of Open-Drain.

1) Level Shifter

(1) Attach a pull-up resistor to the external power supply.

(2) If'Low' is given in Output Control, V_EXT is output to Output.

1) Test

5. Protection circuit using diode (limiter circuit)

1) Looking at the circuits above, you can see that the diode is connected up and down between the output and the MOSFET.

2) When the input voltage exceeds Input + 0.7[V], the diode at the top conducts and goes out to VDD, and the output is output only up to Input + 0.7[V].

3) When the input voltage becomes less than Input-0.7[V], the diode at the bottom conducts and goes out to VSS, and the output is only output up to Input-0.7[V].

6. Orcad is a lite version, so there aren't many parts in pspice. After knowing how to make a library, it was easy, but it was very difficult to find. I'll post the method separately.

7. Anything wrong is welcome.^^