SN74LV14A: the input IO processing circuit use SN74LV14A

Z YM

Part Number: SN74LV14A

Tool/software:

As shown in the figure is the input IO processing circuit, the input switching signal high level is 60V, low level is 0V. The voltage VIN is limited to about 3.5V through D14, the U14(SN74LV14APWR) is supplied to 3.3V, and the Vin and U14 are connected in series with 1K current-limiting resistance.

Question: Although there is a 1K current-limiting resistor, but the U14 input voltage is high than its supply voltage, can this circuit work stably? Does it cause device damage and logic errors?

over 1 year ago

0 Clemens Ladisch over 1 year ago

Guru 316940 points

This device does not have clamping diodes to VCC, so the inputs are overvoltage tolerant, up to 5.5 V. (See [FAQ] Can the input voltage (Vi) to my logic device be higher than the supply voltage (Vcc)?) Voltages above 5.5 V are not clamped, so the 1 kΩ resistor has no effect and would not be able to prevent damage for higher voltages. But your external clamp prevents such high voltages from happening, so this circuit is OK.

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SN74LV14A: the input IO processing circuit use SN74LV14A