Application of TVS diode in the protection circuit, the electronic band you tage of positive solutions!
In the actual circuit, as shown in the figure, in the input DC, sometimes due to changes in the power supply environment will bring some instantaneous pulse. And the best way to eliminate the instantaneous pulse to the device damage, is to lead the instantaneous current from the sensitive device to the ground, the general practice is to TVS on the circuit board and connected in parallel. So, when the instantaneous voltage exceeds the normal working voltage circuit, TVS avalanche breakdown, thus providing instantaneous current of a low impedance path, the result is the instantaneous current is short circuited to GND through TVS, so as to avoid the protected device and restore the normal value before the protected circuit has been cut-off voltage in voltage. And when the instantaneous pulse after the end, TVS diode and then automatically return to the high resistance state, the entire circuit back to the normal voltage state.
Typical circuit topology of TVS diodes
In this paper, we mainly discuss how to apply the TVS tube SMBJ5.0CA and how to make the best application effect by using the example of the typical application circuit in the protection of the hot swap circuit and the protection of the automotive power line. ESD protection grade SMBJ5.0CA with 15KV air discharge and 30KV contact discharge, the response rate of less than 1ps, 600W 10/1000us, duty is less than 0.01% of the peak energy surge energy capacity, and reverse voltage 5V, 65A clamping voltage is 9V, the main electrical characteristics make it very suitable for the protection of the interface.
RS-485 communication is generally used in the intelligent instrument industry. The following figure shows the typical application of RS-485 communication interface. In the protection of the RS-485 interface is not static or surge damage usually make interface protection as shown in Figure 3 using SMBJ5.0CA, or when the electrostatic surge voltage is higher than 5V, SMBJ5.0CA will start action, will the voltage clamp at very low position, if the current exceeds the peak current of IPP, the final voltage will be clamped at about 9V, so as to protect the device level is not damaged.
RS-485 interface protection circuit diagram
The integrated operational amplifier to external electric stress is very sensitive. Therefore, in the process of using the operational amplifier, if due to improper operation or take the normal working conditions, often appear excessive voltage or current, especially the surge and electrostatic pulse, so it is easy to make operational damage or failure. DC power output of 5V, SMBJ5.0CA in the output voltage, the power supply can be used to protect the equipment, but also can absorb the collector of the transistor circuit to the emission peak voltage between the electrodes, thereby protecting the transistor. Therefore, it is suggested that a SMBJ5.0CA tube is added at the output of each voltage stabilized source, which can greatly improve the reliability of the whole machine.
The output stage amplifier protection map
Output level protection of DC regulated power supply
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