definition:
0 ohm, i.e., the resistance value of 0 ohm resistor standard referred 0 ohm. It is an ideal resistor, and the like used for design aspects of PCB
0 ohm has the following features:
1, no function in the circuit, only for debugging design convenience or other reasons compatible on the PCB.
2, can be done by a jumper, both beautiful, but also easy to install. If the lines do not certain, not directly attached to the resistor (not affect the appearance).
3, the matching circuit when the uncertain parameters to 0 ohms instead of actual debugging time, to determine the parameters, and then replaced by elements of specific values.
4, to measure the current consumption of a part of the circuit, they can remove the 0 ohm resistor, connected to the ammeter, the measured current consumption so easy.
5, in the wiring, if it is not passed cloth, may be added to a 0 ohm resistor.
6, the high-frequency signal, serving as inductive or capacitive. (With the external characteristics of the circuit) with inductance, mainly to solve EMC problems. As-ground and ground, and the power supply IC Pin.
7, single-point ground (grounding means protection, grounding, separated from each other in the DC ground equipment, each as an independent system.)
8, do Fuse. Since the PCB traces fusing current is large, if a fault such as short circuit overcurrent occurs, is difficult to fuse, it may lead to more accidents.
0 ohm resistor because the current carrying capacity is relatively weak (actually 0 ohm resistor is a certain, but it is small), on the first overcurrent fuse the 0 ohm, thereby disconnecting the circuit,
It prevents the occurrence of bigger accidents. Some do sometimes fuse with a resistance of a few tenths of a few ohms or less resistance. But this is not recommended to use, but some manufacturers in order to save costs, we will use this the
9, analog and digital ground single point, as long as the ground, will eventually be tied together, and then into the earth. If you are not together is "floating", there is pressure, easy to accumulate electric charge, resulting in static electricity.
0 is the reference potential, the reference voltages are derived for all of the criteria to be consistent, it should be shorted together variously. It is believed that the earth can absorb all the charges, has remained stable, it is the ultimate reference point.
Although some board did not take the land, but power plants are connected to the earth, and power on the board will eventually return to power plants into the ground. If the analog and digital grounds directly connected to a large area, it can cause interference.
And less then wrong, there are four reasons described above resolve this problem: 1, is connected with the magnetic beads; 2, is connected with the capacitor; 3, inductively connected; 4, with a 0 ohm resistor.
Beads equivalent circuit corresponding to a band stop limiter filter, significantly inhibited only a frequency of the noise, it is necessary to use frequency noise estimate, in order to choose the appropriate model.
In the case of frequency uncertain or unpredictable, beads substandard. Cross through the blocking capacitor, resulting in floating. Bulky inductors, multi-parasitics, unstable.
0 ohm corresponding to very narrow current path, the loop current can be effectively restrained, so that noise is suppressed. Resistance on all bands have a damping effect (also 0 ohm impedance), this is stronger than the magnetic beads.
10, when a current loop when divided across electrically * plane, resulting in the shortest return path signal break time, the signal has to pass loop, forming a large loop area, the influence of electric and magnetic fields becomes stronger ,
Easily interfere / interference. Partition straddles the 0 ohm contact can provide a shorter return path, to reduce interference. * * General configuration circuit, do not appear jumpers and DIP switches on the product. Sometimes users will tamper with the setting,
Can lead to misunderstanding, in order to reduce maintenance costs, application 0 ohm jumpers welded in place on the board. Vacant antenna at high frequencies corresponding to the jumper, chip resistors with good effect.
11, when the crossover wires * Other uses debug / test patch device as a temporary substitute for other temperature compensation device
More time is needed for EMC countermeasures.
12, is used as a circuit configuration. This effect DIP switches or jumpers with similar, but fixed by welding up, thus avoiding the ordinary users to freely modify the configuration. Resistance by installing a different location, can change or set the address of the functional circuit.
Further, 0-ohm resistor is smaller than the parasitic inductance of the vias, through-hole and the ground plane will influence (due to the dug)