High-side driver has fault protection

Texas Instruments LP2951

Carl Spearow

EDN

High-side drivers find common use in driving grounded solenoid coils and other loads. Short-circuit protection for such drivers is essential for avoiding damage from wiring faults and other causes. Polymer fuses are generally too slow, and discrete current-limiting circuits are large and cumbersome.

This simple high-side driver provides current limiting as well as transient protection.
Figure 1. This simple high-side driver provides current limiting as well as
transient protection.

The circuit in Figure 1 uses a small, low-dropout linear regulator as a high-side switch and provides inherent current limiting and thermal shutdown. The regulator comes in an SO-8 package. The zener diode provides transient protection, and the output capacitor ensures stability of the circuit. The circuit can drive a 24 V load at 100 mA. These are adequate specs for many solenoid valves, relay coils, and other moderate loads.

In the bottom trace, the output current limits itself to 160 mA during a short circuit.
Figure 2. In the bottom trace, the output current limits itself
to 160 mA during a short circuit.

During a short circuit, the regulator limits the current to 160 mA. This current causes the die to overheat and enter a thermal-shutdown state. Upon removal of the short circuit, the device cools down and resumes normal operation. The top trace in Figure 2 is the output voltage during a 1.3-sec short circuit. The bottom trace is the short-circuit current, which limits itself at less than 200 mA. Note that the regulator goes into thermal shutdown after 500 msec, and the IC then toggles on and off until removal of the short circuit.

Materials on the topic

  1. Datasheet Texas Instruments LP2951

EDN

Price LP2951LP2951 on RadioLocman.Price
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AliExpress25X40BVSIG LP2951CM-3.3 TPH1R403NL TPH1R4 03NL OPA2348A TPS54339E 54339E UC2843 CS4334-KSZR SN74LVC2T45DCTR SP485RE PCF8563T0,20 $
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