Application of TVs tube in maintenance circuit — SUNMATE

The transient voltage suppressor TVs has the characteristics of fast response speed, large transient power, low leakage current, easy control of clamping voltage and small volume under the breakdown and cigarette lighting deviation. At present, TVs tubes have been widely used in communication equipment, AC / DC power supply, cars, household appliances, instruments, new energy and other markets.

In practical circuits, the time of DC input will sometimes bring some instantaneous pulses due to the change of power supply environment. The method to eliminate the harm of instantaneous pulse to equipment is to lead the instantaneous current from sensitive equipment to the ground. Generally, the specific method is to connect TVs in parallel with the maintained circuit on the circuit board. In this way, when the instantaneous voltage exceeds the normal operating voltage of the circuit, TVs will produce avalanche breakdown, and then provide an ultra-low impedance path to the instantaneous current. As a result, the instantaneous current is short circuited to GND through TVs, then avoids the equipment to be maintained, and keeps the cut-off voltage of the circuit to be maintained until the voltage recovers to the normal value. When the instantaneous pulse is completed, the TVS diode will actively recover to the high resistance condition, and the whole circuit will return to the normal voltage condition.

This paper mainly describes the typical application examples in hot plug circuit maintenance and car power line maintenance, and discusses how to correctly use TVs tube smbj5.0ca and how to make it work. Smbj5.0ca has an ESD protection grade of 15kV air discharge and 30KV contact discharge, a response rate of less than 1ps, a peak energy surge energy capacity of 600W of 10/1000us, a duty of less than 0.01%, a reverse operation voltage of 5V, and a clamping voltage of 9V at 65A. These primary electrical characteristics make it very suitable for interface maintenance.

RS-485 communication is generally used in intelligent instrument industry. Typical application of RS-485 communication interface. Smbj5.0ca is usually used to maintain the RS-485 interface from being damaged by static electricity or surge, as shown in Figure 3 below. When the static electricity or surge voltage is higher than 5V, smbj5.0ca will start to act and clamp the voltage at a very low position. If the current exceeds the peak current IPP, the final voltage will be clamped at about 9V, and then the equipment after maintenance will not be damaged.

The integrated operational amplifier is very sensitive to external electrical stress. Therefore, in the process of using the operational amplifier, if the operation is wrong or abnormal operating conditions are adopted, there will often be excessive voltage or current, especially surge and electrostatic pulse, and then the operational amplifier will be easily damaged or invalid. For a 5V output DC regulated power supply, smbj5.0ca is added to its regulated output end to maintain the instruments and equipment using the power supply. It can also absorb the peak voltage from the collector to the emitter of the transistor in the circuit, and then maintain the transistor. Therefore, it is proposed to add an smbj5.0ca tube at the output end of each stabilized voltage source, which can greatly improve the reliability of the whole machine.