PCB Layout Design Specifications——Circuit Design (2)

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PCB Layout Design Specifications——Circuit Design (2) [Copy link]

PCB Layout Design Specifications - Circuit Design (2)

161. Clarify the maximum operating frequency of each board, and take necessary shielding measures for devices or components with an operating frequency above 160MHz (or 200 MHz) to reduce their radiation interference level and improve their ability to resist radiation interference

162. If possible, add RC decoupling at the entrance of the control line (on the printed circuit board) to eliminate interference factors that may occur during transmission. 163. If possible, add RC decoupling at the entrance of the control line (on the printed board) to eliminate possible interference factors that may occur during transmission. 164. Use fast recovery diodes in the secondary rectification circuit or connect polyester film capacitors in parallel with the diodes. 165. “Shape” the transistor switching waveform. 166. Reduce the input impedance of sensitive lines. 167. If possible, use balanced lines as input for sensitive circuits, and use the inherent common-mode suppression capability of balanced lines to overcome the interference of interference sources on sensitive lines. 168. It is inappropriate to directly ground the load. 169. Pay attention to adding bypass decoupling capacitors (usually 104) between the power supply and ground near the IC. 170. If possible, use balanced lines as input for sensitive circuits, and the balanced lines are not grounded.

171. A freewheeling diode is added to the relay coil to eliminate the back electromotive force interference generated when the coil is disconnected. Only adding a freewheeling diode will delay the disconnection time of the relay. After adding a voltage-stabilizing diode, the relay can operate more times per unit time. 172. Connect a spark suppression circuit (usually an RC series circuit, with a resistor of several K to tens of K and a capacitor of 0.01uF) in parallel at both ends of the relay contact to reduce the impact of electric sparks. 173. Add a filter circuit to the motor, and pay attention to the short leads of the capacitor and inductor as much as possible. 174. Each IC on the circuit board should be connected in parallel with a 0.01μF~0.1μF high-frequency capacitor to reduce the impact of the IC on the power supply. Pay attention to the wiring of the high-frequency capacitor. The connection should be close to the power supply end and as thick and short as possible. Otherwise, it is equivalent to increasing the equivalent series resistance of the capacitor, which will affect the filtering effect. 175. Connect an RC suppression circuit at both ends of the thyristor to reduce the noise generated by the thyristor (this noise may break down the thyristor when it is serious) 176. Many microcontrollers are very sensitive to power supply noise. It is necessary to add a filter circuit or a voltage regulator to the microcontroller power supply to reduce the interference of power supply noise on the microcontroller. For example, a π-shaped filter circuit can be formed by using magnetic beads and capacitors. Of course, if the conditions are not high, a 100Ω resistor can be used instead of a magnetic bead.

177. If the I/O port of the microcontroller is used to control noisy devices such as motors, isolation should be added between the I/O port and the noise source (add a π-shaped filter circuit). To control noisy devices such as motors, isolation should be added between the I/O port and the noise source (add a π-shaped filter circuit).

178.Using anti-interference components such as magnetic beads, magnetic rings, power filters, and shielding covers at key locations such as the microcontroller I/O port, power line, and circuit board connection line can significantly improve the circuit's anti-interference performance. 179. For the idle I/O ports of the microcontroller, do not leave them floating, but connect them to the ground or power supply. The idle ends of other ICs can be grounded or connected to the power supply without changing the system logic. 180. Using power monitoring and watchdog circuits for microcontrollers, such as: IMP809, IMP706, IMP813, X25043, X25045, etc., can greatly improve the anti-interference performance of the entire circuit. 181. Under the premise that the speed can meet the requirements, try to reduce the crystal oscillator of the microcontroller and choose a low-speed digital circuit. 182. If possible, add RC low-pass filters or EMI suppression components (such as magnetic beads, signal filters, etc.) at the interface of the PCB board to eliminate the interference of the connecting wires; but be careful not to affect the transmission of useful signals. 183. When routing clock outputs, do not use direct serial connections to multiple components (called daisy-chaining); instead, provide clock signals directly to multiple components through buffers. 184. Extend the edge of the membrane keyboard to extend 12mm beyond the metal wire, or use plastic cutouts to increase the path length. 185. Connect the signal on the connector to the chassis ground of the connector using an LC or bead-capacitor filter near the connector. 186. Add a magnetic bead between the chassis ground and the circuit common ground. 187. The power distribution system inside the electronic equipment is the main object of ESD arc inductive coupling. The anti-ESD measures for the power distribution system are: 1 Twist the power line and the corresponding return line tightly together; 2 Place a magnetic bead at the place where each power line enters the electronic equipment; 3 Place a transient current suppressor, metal oxide varistor (MOV) or 1kV high-frequency capacitor between each power pin and the chassis ground close to the electronic equipment; 4 It is best to arrange a dedicated power and ground plane on the PCB, or a tight power and ground grid, and use a large number of bypass and decoupling capacitors. 188. Place resistors and ferrite beads in series at the receiving end. For cable drivers that are easily hit by ESD, you can also place resistors or ferrite beads in series at the driving end. 189. Place a transient protector at the receiving end. 1 Use a short and thick wire (less than 5 times the width, preferably less than 3 times the width) to connect to the chassis ground. 2 The signal line and ground line coming out of the connector should be directly connected to the transient protector before connecting to other parts of the circuit. 190. Place filter capacitors at the connector or within 25 mm (1.0 inch) of the receiving circuit. 1 Use short, thick wires to connect to the chassis ground or receiving circuit ground (less than 5 times the width, preferably less than 3 times the width). 2 Connect the signal line and ground wire to the capacitor first and then to the receiving circuit.If possible, add RC low-pass filters or EMI suppression components (such as magnetic beads, signal filters, etc.) at the interface of the PCB board to eliminate interference from the connecting lines; but be careful not to affect the transmission of useful signals. 183. When wiring the clock output, do not use direct serial connections to multiple components (called daisy-chain connection); instead, provide clock signals directly to multiple other components through buffers. 184. Extend the border of the membrane keyboard to extend it 12mm beyond the metal wire, or use plastic cuts to increase the path length. 185. Near the connector, use an LC or bead-capacitor filter to connect the signal on the connector to the chassis ground of the connector. 186. Add a bead between the chassis ground and the circuit common ground. 187. The power distribution system inside the electronic equipment is the main object to suffer from the inductive coupling of ESD arc. The anti-ESD measures for the power distribution system are: 1 Twist the power line and the corresponding return line tightly together; 2 Place a magnetic bead at the place where each power line enters the electronic equipment; 3 Place a transient current suppressor, metal oxide varistor (MOV) or 1kV high-frequency capacitor between each power pin and the ground close to the electronic equipment chassis; 4 It is best to arrange dedicated power and ground planes, or tight power and ground grids on the PCB, and use a large number of bypass and decoupling capacitors. 188. Place resistors and ferrite beads in series at the receiving end. For cable drivers that are easily hit by ESD, you can also place resistors or ferrite beads in series at the driving end. 189. Place a transient protector at the receiving end. 1 Use a short and thick wire (less than 5 times the width, preferably less than 3 times the width) to connect to the chassis ground. 2 The signal line and ground line coming out of the connector should be directly connected to the transient protector before connecting to other parts of the circuit. 190. Place filter capacitors at the connector or within 25 mm (1.0 inch) of the receiving circuit. 1 Use short, thick wires to connect to the chassis ground or receiving circuit ground (less than 5 times the width, preferably less than 3 times the width). 2 Connect the signal line and ground wire to the capacitor first and then to the receiving circuit.If possible, add RC low-pass filters or EMI suppression components (such as magnetic beads, signal filters, etc.) at the interface of the PCB board to eliminate interference from the connecting lines; but be careful not to affect the transmission of useful signals. 183. When wiring the clock output, do not use direct serial connections to multiple components (called daisy-chain connection); instead, provide clock signals directly to multiple other components through buffers. 184. Extend the border of the membrane keyboard to extend it 12mm beyond the metal wire, or use plastic cuts to increase the path length. 185. Near the connector, use an LC or bead-capacitor filter to connect the signal on the connector to the chassis ground of the connector. 186. Add a bead between the chassis ground and the circuit common ground. 187. The power distribution system inside the electronic equipment is the main object to suffer from the inductive coupling of ESD arc. The anti-ESD measures for the power distribution system are: 1 Twist the power line and the corresponding return line tightly together; 2 Place a magnetic bead at the place where each power line enters the electronic equipment; 3 Place a transient current suppressor, metal oxide varistor (MOV) or 1kV high-frequency capacitor between each power pin and the ground close to the electronic equipment chassis; 4 It is best to arrange dedicated power and ground planes, or tight power and ground grids on the PCB, and use a large number of bypass and decoupling capacitors. 188. Place resistors and ferrite beads in series at the receiving end. For cable drivers that are easily hit by ESD, you can also place resistors or ferrite beads in series at the driving end. 189. Place a transient protector at the receiving end. 1 Use a short and thick wire (less than 5 times the width, preferably less than 3 times the width) to connect to the chassis ground. 2 The signal line and ground line coming out of the connector should be directly connected to the transient protector before connecting to other parts of the circuit. 190. Place filter capacitors at the connector or within 25 mm (1.0 inch) of the receiving circuit. 1 Use short, thick wires to connect to the chassis ground or receiving circuit ground (less than 5 times the width, preferably less than 3 times the width). 2 Connect the signal line and ground wire to the capacitor first and then to the receiving circuit.0 inches), place the filter capacitor. 1 Use a short and thick wire to connect to the chassis ground or the receiving circuit ground (the length is less than 5 times the width, preferably less than 3 times the width). 2 The signal line and ground wire are first connected to the capacitor and then to the receiving circuit.0 inches), place the filter capacitor. 1 Use a short and thick wire to connect to the chassis ground or the receiving circuit ground (the length is less than 5 times the width, preferably less than 3 times the width). 2 The signal line and ground wire are first connected to the capacitor and then to the receiving circuit.

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Good summary.