Methods to improve the anti-interference ability of electronic circuits:
One, reduce the noise from the power supply
Power supply to the system to provide energy at the same time, but also its noise added to the power supply. The reset line of the microcontroller in the circuit, the interrupt line, as well as some other control lines are most susceptible to interference from external noise.
Strong interference from the power grid enters the circuit through the power supply. Even in battery-powered systems, the battery itself has high-frequency noise. Analog signals in analog circuits are even more vulnerable to interference from the power supply. Therefore, the design of the power supply to take certain anti-interference measures: (such as input power and power equipment power lines separate; the use of isolation transformers; the use of low-pass filters; the use of independent function block separate power supply, etc.).
Two, reduce the distortion in the signal transmission
Microcontrollers are mainly manufactured using high-speed CMOS technology. Signal input static input current in about 1mA, input capacitance of about 10pF, the input impedance is quite high. The outputs of high-speed CMOS circuits have considerable bandwidth capacity, i.e., a fairly large output value, and the reflection problem is serious when the output of a gate is led through a very long line to an input with a fairly high input impedance. It causes signal distortion and increases system noise. When Tpd>Tr, it becomes a transmission line problem, and signal reflections, impedance matching, etc. must be considered.
The delay time of a signal on a printed circuit board is related to the characteristic impedance of the leads, i.e. to the dielectric constant of the printed circuit board material. It can be roughly assumed that the transmission speed of the signal on the printed board leads is between about 1/3 and 1/2 the speed of light. The Tr (standard delay time) of logic electronics commonly used in systems composed of microcontrollers is between 3 and 18ns.
On a printed wiring board, where the signal passes through a 7W resistor and a 25cm long piece of lead, the delay time on the wire is roughly between 4 and 20ns. That is to say, the signal on the printed circuit of the shorter the better, the longest should not exceed 25cm, and the number of holes should be as small as possible, preferably no more than two.
When the rise time of the signal is faster than the signal delay time, according to the fast electronics processing. At this time to consider the impedance matching of the transmission line, for a printed circuit board on the integrated block between the signal transmission, to avoid the Td>Trd situation, the larger the printed circuit board the speed of the system can not be too fast.
Using the following conclusion to summarize a rule of printed wiring board design: signal transmission on the printed circuit board, its delay time should not be greater than the nominal delay time of the device used.
-Power supply circuits: generate the required power supply for various electronic circuits.
-Electronic circuit: also known as electrical circuit.
-Base Frequency Circuit, base frequency, low frequency, using base frequency components.
-High-frequency circuits, high-frequency, high-frequency, using high-frequency components.
-Base frequency, high frequency hybrid circuits
-Passive components: such as resistors, capacitors, inductors, diodes ... etc., there are base frequency passive components, high frequency passive components.
-Active components: such as transistors, microprocessors ... and so on, there are base-frequency active components, high-frequency active components.
Microprocessor circuits: Also known as microcontroller circuits, they form the basis for computers, game consoles, (players, video, audio), various home appliances, mice, keyboards, touch controls...and so on.
Computer circuits: Advanced microprocessor circuits for desktop computers, notebook computers, handheld computers, industrial computers, and various other computers.
Communication circuits: Formation of telephone, cellular phone, wired network, wired transmission, wireless network, wireless transmission, optical communication, infrared, fiber optic, microwave communication, satellite communication, and so on.
Display circuit: the formation of the screen, TV, meters and other types of displays.
Optoelectronic circuits: such as solar energy circuits.
Motor circuits: Often used in large power supply equipment, such as electric power equipment, transportation equipment, medical equipment, industrial equipment, etc..
Series circuits: A connection in which the same current passes through all connected devices
Parallel circuits: A connection in which the same voltage is applied to all connected devices
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