Problems with the MCU IO port control negative voltage circuit

Knight97538

Problems with the MCU IO port control negative voltage circuit [Copy link]

The following circuit should be able to control the on and off of -5V, right?

If so, can transistor U7 be omitted?

What are the benefits of adding this transistor?

Why not, listen to what everyone says

maychang

[The following circuit should be able to control the on and off of -5V, right? ]

Can.

When GPIO7 is at a high level, U7 is turned on and the MOS tube is turned on.

maychang

[If so, can transistor U7 be omitted? ]

Transistor U7 cannot be omitted.

maychang

What are the benefits of adding this transistor?

There is no benefit in adding a transistor. Without this transistor, the MOS tube cannot control the -5V on and off.

maychang

【Why not, let’s hear what everyone says】

The word "maybe" is really redundant.

dabiaoke

The GPIO port is used to control the on and off of the transistor so that the Vgs voltage is 5V or 0V, thereby controlling the -5V output. There is no problem with the circuit, but the transistor cannot be omitted, otherwise the instantaneous driving capability of the GPIO port may be insufficient.

Knight97538

maychang posted on 2023-2-23 12:08 [The following circuit should be able to control the on and off of -5V, right? ] Yes. When GPIO7 is at a high level, U7 is turned on and the MOS tube is turned on.

If it is because GPIO7 is high, U7 is turned on and MOS is turned on

GPIO7 can be set to low level anytime and anywhere, this reason is not sufficient

Knight97538

dabiaoke posted on 2023-2-23 20:06 The GPIO port is used to control the conduction and shutdown of the transistor so that the Vgs voltage is 5V or 0V, thereby controlling the -5V output. There is no problem with the circuit, but the transistor is not...

Is the purpose of the transistor to increase driving force?

maychang

Knight97538 posted on 2023-2-24 13:34 Is the purpose of the triode to increase driving force?

[Is the purpose of the triode to increase driving force?]

It is not only to increase the driving capability, but more importantly to change the voltage level. The voltage range of GPIO7 is 0V~5V or 0V~3.3V, and the addition of the transistor changes it to 5V~0V.

This is exactly why I said on the 4th floor, "There is no benefit in adding the transistor. Without this transistor, the MOS tube cannot control the on and off of -5V."

maychang

Knight97538 posted on 2023-2-24 13:33 If U7 is turned on because GPIO7 is at a high level, and MOS is turned on, it can make GPIO7 low at any time. This reason is not sufficient

[GPIO7 can be set to low level anytime and anywhere, this reason is not sufficient]

If there is no transistor, GPIO7 is at a low level and the MOS tube cannot be turned off. If it cannot be turned off, how can we talk about [control]?

maychang

Knight97538 posted on 2023-2-24 13:33 If U7 is turned on because GPIO7 is at a high level, and MOS is turned on, it can make GPIO7 low at any time. This reason is not sufficient

I only said [when GPIO7 is high, U7 is turned on, and the MOS tube is turned on] on the second floor, but did not say [when GPIO7 is low, U7 is turned off, and the MOS tube is turned off]. I thought you could change [high level] to [low level], and [on] to [off]. I didn't expect you don't have this ability.