High-impedance Mode

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High-impedance Mode

High-impedance mode is a common term in a digital circuit. It refers to an output state of a circuit. It is neither high nor low. If a high-impedance state is input into a lower-level circuit, there is no impact on the lower-level circuit, and it is the same as not connected. If you use a multimeter for testing, it may be high or low, depending on what is next to it.

Essence of the high-impedance mode:

When the circuit is analyzed, the high blocking state can be understood as an open circuit. You can think of it as a very large output (input) resistor. His limit can be considered to be suspended. That is to say, in theory, the high-impedance state is not suspended. It is a State with great resistance to the ground or power supply. The actual application is almost the same as the pin suspension.

Significance of the high-impedance mode:

When the output of the door circuit is turned on and the drop-down tube ends, the output is high; the opposite is low; when the above drop-down tube and drop-down tube are both ended, the output end is equivalent to floating (no current flow), and its level varies with the external level, that is, the circuit gives up the control of the output end circuit.

Typical applications:

1,In the structure of the bus connection. There are multiple devices mounted on the bus, and the devices are connected to the bus in the form of high resistance. In this way, the bus is automatically released when the device does not occupy the bus to facilitate other devices to obtain the right to use the bus.

2,Most single-chip I/O applications can be set to high-impedance input, such as lingyang and AVR. High-impedance input can be considered as infinite input resistance, and I/O has a very small impact on the front-level without generating current (no attenuation ), to some extent, it also increases the chip's ability to resist voltage impact.

Common representation of high-impedance states

The letter Z is commonly used in the high-impedance mode.