(1) Adding TVS diodes to signal and power lines can prevent microprocessors or single-chip microcomputers from malfunctioning due to instant fat rush, such as electrostatic discharge effects, surges of AC power and noise of switching power supplies.
(2) The electrostatic discharge effect can release pulses exceeding 10000V and 60A and last for 10ms; while general TTL devices will be damaged when they encounter 10V pulses exceeding 30ms. The use of TVS diodes can effectively absorb pulses that can cause device damage, and can eliminate interference (Crosstalk) caused by switching between buses.
(3) Placing the TVS diode between the signal line and the ground can prevent the data and control bus from being affected by unnecessary noise.
Selection skills of TVS diodes
(1) Determine the maximum DC or continuous operating voltage of the protected circuit, the rated standard voltage of the circuit, and the “high side” tolerance.
(2) The rated reverse turn-off VWM of the TVS should be greater than or equal to the maximum working voltage of the protected circuit. If the selected VWM is too low, the device may enter an avalanche or affect the normal operation of the circuit due to excessive reverse leakage current. The serial connection divides the voltage, and the parallel connection divides the current.
(3) The maximum clamping voltage VC of TVS should be less than the damage voltage of the protected circuit.
(4) During the specified pulse duration, the maximum peak pulse power consumption PM of TVS must be greater than the peak pulse power that may appear in the protected circuit. After determining the maximum clamping voltage, its peak pulse current should be greater than the transient surge current.
(5) For the protection of the data interface circuit, attention must also be paid to selecting a TVS device with a suitable capacitance C.
(6) Select the polarity and package structure of TVS according to the application. It is more reasonable to choose bipolar TVS for AC circuit; it is more beneficial to choose TVS array for multi-line protection.
(7) Temperature consideration. The transient voltage suppressor can work between -55℃～+150℃. If the TVS is required to work at a changing temperature, because its reverse leakage current ID increases with the increase; the power consumption decreases with the increase of the TVS junction temperature, from +25°C to +175°C, about a linear drop of 50% rain strike The breakdown voltage VBR increases by a certain coefficient with the increase of temperature. Therefore, it is necessary to consult the relevant product information and consider the effect of temperature changes on its characteristics.
The best way to deal with transient pulse damage to the element is to divert the transient current away from the sensing element. The TVS diode is connected in parallel with the protected circuit on the circuit board. When the instantaneous voltage exceeds the normal operating voltage of the circuit, the TVS diode will generate an avalanche, providing an ultra-low resistance path for the instantaneous current. As a result, the instantaneous current is drawn through the diode. Avoid the protected components and keep the protected circuit at the cut-off voltage until the voltage returns to normal. When the transient pulse ends, the TVS diode automatically returns to the high-impedance state, and the entire circuit enters the normal voltage. Many components will degrade their parameters and performance after being subjected to multiple shocks, but diodes will not be damaged or degraded as long as they are operated within limits.
Post time: Jun-15-2022