How to analyze this circuit

kal9623287

How to analyze this circuit [Copy link]

What does it mean to connect the two resistors in the dotted box like this?

What is the role of GDT here?

Are there any other ways to connect the two grounds like the one in the red box?

呜呼哀哉

This three-legged gas discharge tube is equivalent to two independent ones, with AB lines connected to the ground. The resistor and capacitor in the red frame are for static discharge and anti-static, and can be placed anywhere. The two dotted lines are for a fixed input of the differential signal, so that when it is not connected later, the digital circuit input will not float and jump randomly.

maychang

"What does it mean to connect these two resistors in the dotted box like this?"

This is a differential signal transmission line like 485. The two resistors in the dotted box are obviously used to pull up line A and pull down line B.

maychang

What is the purpose of GDT here?

When the voltage between the two signal lines and the ground is too high, the GDT will discharge to limit the voltage between the two lines and the ground.

chunyang

The dotted line is the bus static bias resistor, the purpose of which is to bias the bus static level to the logic 1 level when the bus is idle.

The purpose of the discharge tube is to discharge the high voltage sensed by the bus to protect the bus interface components.

The discharge circuit of the protection element must be the so-called "protective ground", which must be connected in this way, and there is no "other way". In applications where no protection is required, there is naturally no protective ground.

kal9623287

Alas, published on 2022-12-5 13:35 This three-legged gas discharge tube is equivalent to two independent ones, with the AB line facing the ground. The resistor and capacitor in the red frame are for static discharge and anti-static. What position...

Can one of R1 and C2 be removed?

Or is there any other way