SN74LVC1G17, in our application, we use 3.3V for Vcc. The logic input can be as high as 5V. Is this part 5V tolerant for input ?
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For an explanation as to why, please see: [FAQ] Can the input voltage (Vi) to my logic device be higher than the supply voltage (Vcc)?
Sorry, I forgot to answer your question!
Yes, as I said at the start, the device has over-voltage tolerant inputs. This means that there is no input clamp diode and current will not flow from the input to the Vcc pin.
It would definitely help me if you can identify what I can do to make this more clear -- I'd like to improve our FAQ at least to avoid confusion, as this continues to be one of our most asked questions on the forums.
M liu said:
The data sheet of SN74LVC1G17 does NOT mention anything about positive clamp diode
Thanks for the input. We are working to add explicit statement of the clamp diode placements for all released datasheets going forward, but older datasheets like this one may take a long time to be updated. In the meantime, the FAQ I provided explains how to determine this in detail for any device.
Although the datasheet doesn't use the words "positive clamp diode," it does include specs that identify the existence of the diode in both the absolute maximum ratings table and the recommended operating conditions tables.
The input voltage range (first highlight) does not indicate a dependence of input voltage on VCC (max), which means there's no positive clamp diode. This is confirmed by the Input clamp current (clamp meaning clamp diode), which only shows activating the clamp diode when the input voltage is less than 0V -- thus indicating only a negative side diode.
Double checking in the recommended operating conditions table, we can see the input voltage repeated with no dependence on VCC:
M liu said:
also, for the input signal for this chip, for Vcc = 3.3V, what is the minimum Vin level to be a HI input ? the dats sheet has Vcc= 3V only. Thanks
For a Schmitt-trigger buffer you need to exceed the maximum positive threshold value to guarantee a 'high' input. You can use linear interpolation to determine the minimum VIH for a "high" level input to be guaranteed based on the provided datasheet values as described in this FAQ: [FAQ] What method is best used for estimating specification values between those given in the datasheet?
Given the datasheet values for VT+ at 3V (1.92) and 4.5V (2.74), I calculate 2.084V at 3.3V.