MC3423 DATASHEET PDF

The threshold or trip voltage at which the MC will trigger and supply gate drive to the crowbar SCR, Q1, is determined by the selection of R1 and R2. Their values can be determined by the equation given in Figures 3 and 4, or by the graph shown in Figure 8. The minimum value of the gate current limiting resistor, RG, is given in Figure 9. If lower output currents are required, RG can be increased in value. The switch, S1, shown in Figure 3 may be used to reset the crowbar.

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The threshold or trip voltage at which the MC will trigger and supply gate drive to the crowbar SCR, Q1, is determined by the selection of R1 and R2. Their values can be determined by the equation given in Figures 3 and 4, or by the graph shown in Figure 8. The minimum value of the gate current limiting resistor, RG, is given in Figure 9. If lower output currents are required, RG can be increased in value.

The switch, S1, shown in Figure 3 may be used to reset the crowbar. Otherwise, the power supply, across which the SCR is connected, must be shut down to reset the crowbar. The circuit configurations shown in Figures 3 and 4 will have a typical propogation delay of 1. If faster operation is desired, Pin 3 may be connected to Pin 2 with Pin 4 left floating. This will result in decreasing the propogation delay to approximately 0. To prevent false tripping of the OVP circuit by noise which would not normally harm the load, MC has a programmable delay feature.

To implement this feature, the circuit configuration of Figure 5 is used. In this configuration, a capacitor is connected from Pin 3 to VEE. The value of this capacitor determines the minimum duration of the overvoltage condition which is necessary to trip the OVP. The value of C can be found from Figure The circuit operates in the following manner: When VCC rises above the trip point set by R1 and R2, an internal current source Pin 4 begins charging the capacitor, C, connected to Pin 3.

Occasionally, it is desired that immediate crowbarring of the supply occur when a high overvoltage condition occurs, while retaining the false tripping immunity of Figure 5. In this case, the circuit of Figure 6 can be used.

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MC3423 ON Semiconductor, MC3423 Datasheet

Features, Applications This overvoltage protection circuit OVP protects sensitive electronic circuitry from overvoltage transients or regulator failures when used in conjunction with an external "crowbar" SCR. The device senses the overvoltage condition and quickly "crowbars" or short circuits the supply, forcing the supply into current limiting or opening the fuse or circuit breaker. The protection voltage threshold is adjustable and the MC can be programmed for minimum duration of overvoltage condition before tripping, thus supplying noise immunity. The MC is essentially a "two terminal" system, therefore it can be used with either positive or negative supplies. AN : Quadruple Operational Amplifiers. They have electrical characteristics equal to the conventional operational amplifiers, and are low powered and suitable for application to various.

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