SN74LVC1G34: SN74LVC1G34 powered by 3.3V supply with 1.8V input signal

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Part Number: SN74LVC1G34
Other Parts Discussed in Thread: SN74LV1T34

Tool/software:

Initially I was using SN74LV1T34 (that can work with 1.8V input and 3.3V supply) but switched to SN74LVC1G34 for higher output current.

Recommended Vih is 2V, but the device still works for some reason with 1.8V input, any ideas ?

1 month ago

0 Albert Xu1 1 month ago

TI__Mastermind 37845 points

Hi,

You cannot have an input signal between the VIL and VIH thresholds. This state is an unknown state in the device and can lead to permanent damage.

Please refer to this FAQ: [FAQ] How does a slow or floating input affect a CMOS device?

0 Clemens Ladisch 1 month ago

Guru 316690 points

The device will switch somewhere between V_IL and V_IH. In your test, the actual threshold was below 1.8 V, but there is no guarantee that this will always be the case. And for voltages below V_IH, even when the output is 'correctly' high, you will get the negatice effects described in the FAQ

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SN74LVC1G34: SN74LVC1G34 powered by 3.3V supply with 1.8V input signal