The Application of TVS diode in Circuit Maintenance

The Application of TVS diode in Circuit Maintenance

The transient voltage suppression diode (TVS) has the characteristics of fast response speed, high transient power, low leakage current, easy operation of clamping voltage under breakdown cigarette deviation, and small size. Nowadays, TVS diode have been widely used in communication equipment, AC/DC power supplies, cars, household appliances, instruments, new energy and other markets.

In practical circuits, during DC input, sometimes changes in the power supply environment may cause some instantaneous pulses. The method to eliminate the harm of instantaneous pulses to equipment is to lead the instantaneous current from the sensitive equipment to the ground. The general specific method is to connect the TVS in parallel with the maintained line on the circuit board. In this way, when the instantaneous voltage exceeds the normal operating voltage of the circuit, TVS will experience avalanche breakdown and provide an ultra-low impedance path for the instantaneous current. The result is that the instantaneous current is short circuited to GND through TVS, avoiding the equipment being maintained, and maintaining the cut-off voltage of the maintained circuit until the voltage recovers to normal. After the instantaneous pulse is completed, the TVS diode actively recovers to a high resistance condition, and the entire circuit returns to normal voltage conditions.

This article mainly describes typical examples of circuit applications in hot swappable circuit maintenance and car power cord maintenance, and specifically discusses how to correctly use TVS diode SMBJ5.0CA and how to achieve its application effect. SMBJ5.0CA has an ESD protection level 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, and a duty of less than 0.01%. The reverse operating voltage is 5V, and the clamping voltage at 65A is 9V. These primary electrical characteristics make it very suitable for interface maintenance.

In intelligent instrument professions, RS-485 communication is generally used. Typical application of RS-485 communication interface. When maintaining the RS-485 interface, it is not damaged by static electricity or surge, usually SMBJ5.0CA is used for interface maintenance, as shown in Figure 3 below. When the static electricity or surge voltage is higher than 5V, SMBJ5.0CA will start to act and place the Voltage clamp 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 an operational amplifier, if due to operational errors or abnormal operating conditions, excessive voltage or current, especially surges and electrostatic pulses, are often present, which can easily cause damage or failure of the operational amplifier. A 5V output DC regulated power supply, with SMBJ5.0CA added to its regulated output, can maintain the instrument equipment using this power supply, and can also absorb the peak voltage between the collector and emitter of the transistor in the circuit, and then maintain the transistor. Therefore, it is advocated to add an SMBJ5.0CA transistor to the output end of each voltage regulator, which can greatly improve the reliability of the entire machine.