In the circuit board design, when two points cannot be connected by circuits. They are often connected by jumpers. This is often seen in ordinary boards. In order to make the automatic placement machine and automatic plug-in machine work normally, zero ohm resistor is used to replace the jumper.
The summary of the functions of zero ohm resistor can include the following:
1. There is no function in the circuit, just for debugging convenience or compatible design on the PCB.
2. Can be used as a jumper to avoid high-frequency interference caused by jumpers (becoming an antenna)
3. When the circuit parameters are uncertain, replace it with 0 ohms. In actual debugging, determine the parameters and replace them with specific components.
4. 0 ohm resistor is actually a resistor with a very small resistor value. When you want to measure the current consumption of a certain part of the circuit, connect a 0 ohm resistor with an ammeter, so that it is convenient to measure the current consumption and can be used to measure large currents.
5. When PCB layout, if it is really not feasible use a line to cross, you can also add a 0 ohm resistor to cross.
6. Under high frequency signals, it acts as an inductor or a capacitor. (Related to external circuit characteristics) Inductance is mainly used to solve EMC problems. Such as between ground and ground, power supply and IC Pin.
7. Single-point grounding (protective grounding, working grounding, and DC grounding are separated from each other on the equipment, and each becomes an independent system.)
8. Configure the circuit, engineers do not want jumpers and DIP switches on products. Sometimes users will change the settings randomly, which is easy to cause error on PCB. In order to reduce maintenance costs, 0 ohm resistors are used instead of jumpers to be soldered on the board.
9. For circuit protection, it acts as a low-cost fuse. Due to the large fusing current of the line on the PCB, it is difficult to fuse if a short-circuit or over-current fault occurs. It may cause bigger accidents.
Since 0 ohm resistor overload current is relatively small (in fact, 0 ohm resistor also has a certain resistor, but it is very small), the 0 ohm resistor is first fused when overcurrent, thereby disconnecting the circuit and preventing greater accidents happened. Sometimes small resistors with a resistor value of a few tenths or a few ohms are used as fuses. However, this is not recommended, but some manufacturers just use it in order to save costs.
In mixed circuits such as digital and analog, the two grounds are often required to be separated and connected at a single point. We can use a 0 ohm resistor to connect the two grounds instead of directly connecting them together. The advantage of this is that the ground wire is divided into two networks, which is much more convenient when add large areas of copper. Incidentally, in such cases, inductors or magnetic beads are sometimes used for connection.
How much current can a zero-ohm resistor withstand? Zero-ohm resistors are often used in circuit design. Generally, the rated power of the resistor is selected according to the current. So which package is the appropriate for 0 ohm?
The actual resistor value of a general 0 ohm resistor is about +-5% deviation, about 50 milliohms. So based on the rated power, you can calculate its rated current.
0402 1/16W: 1/16=I*I*0.05 i.e. I=1.118A;
0603 1/8W: 1/8=I*I*0.05 i.e. I=1.58A;
0805 1/4W: 1/4=I*I*0.05 ie I=2.236A;
For each package, how much current the 0 ohm resistor can pass through is also determined according to the heat dissipation of the resistor on the PCB board.
The relationship between the current and the voltage across the resistor under three packages of 0603, 0805, and 1206 are tested below. It can be seen that the voltage of the three packages begins to rise rapidly after the current actually exceeds 6A.
This shows that the temperature of the resistor has also increased sharply, leading to a significant increase in power consumption. The resistor of 0603 burned when the current increased to 11.5A, the resistor of 0805 burned when the current increased to 12A, and the resistor of 1206 was not burned when the current was 12A.
Current and voltage curve of 0603 package 0 ohm resistance
Current and voltage curve of 0805 package 0 ohm resistance
Current and voltage curve of 1206 package 0 ohm resistance