![]() As it's quite a versatile device, for your convenience you can view or download the IRF7319 datasheet here: The package includes ultra-low ON resistance N- and P-MOSFETs. The input voltage is limited by the maximum gate-source voltage, V GS, of the MOSFETs, which is 20V – so I recommend a maximum input voltage of 18V, allowing a safety margin of 2V.īoth N-type and P-type MOSFETs are provided in a single SMD package as part number IRF7319 1), making the circuit's total real estate requirement minimal. The R DS-ON of the P-MOSFET used as the high-side switch is only 0.058 ohms so its small surface mount package doesn't heat much, even at currents of 4 amp. ![]() For it to reliably turn OFF, the load should draw sufficient current so that any downstream capacitors will discharge within a few seconds, allowing the gate drive of the N-MOSFET to decay. While it is ON, pressing and holding the button for more than 3 seconds turns the power switch back OFF, and it stays OFF until the next momentary button press. When in its OFF state, momentarily pressing the tactile button turns ON the switched power and it latches ON, supplying power to the output. And that power is minimal the P-MOSFET has an ON resistance of only 58 milli-Ω. ![]() Even in the ON state the circuit draws very little bias current to maintain its latched state – only the series pass transistor dissipates some power as it passes the load current. In the initial OFF state, this circuit uses no power – the only current drawn is the sub-microamp reverse leakage currents of the diode and the MOSFETs.
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