| Electronics > Beginners |
| Logic Level Shifters? |
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| Zero999:
--- Quote from: theatrical scene on January 22, 2019, 02:22:58 am --- --- Quote from: oPossum on January 22, 2019, 02:17:18 am --- --- Quote from: theatrical scene on January 22, 2019, 02:06:23 am --- The RPi has uses both inputs and outputs which means I would need to get both the 74HCT and 74AHC parts right (for low-high level shifting and high-low)? --- End quote --- Yes. Forgot to mention the 74xxx541. That has a pinout that can be easier to work with than the 74xxx244. --- End quote --- Thanks, is there a version of this (or similar part) with 6-8 buffers built into a single package? --- End quote --- Replace the xxx in those part numbers with HCT, for low to high and AHC for high to low. The 74xxx14 is a good hex inverting buffer and has Schmitt trigger inputs. |
| FrankBuss:
--- Quote from: theatrical scene on January 22, 2019, 02:22:58 am --- --- Quote from: oPossum on January 22, 2019, 02:17:18 am --- --- Quote from: theatrical scene on January 22, 2019, 02:06:23 am --- The RPi has uses both inputs and outputs which means I would need to get both the 74HCT and 74AHC parts right (for low-high level shifting and high-low)? --- End quote --- Yes. Forgot to mention the 74xxx541. That has a pinout that can be easier to work with than the 74xxx244. --- End quote --- Thanks, is there a version of this (or similar part) with 6-8 buffers built into a single package? --- End quote --- 74LVC8T245 has 8 buffers, and one pin to decide the direction control, which you can just tie to VCC(A) or GND for a fixed direction. |
| Zero999:
There's also the CD40109B, which is slow but can come in handy, especially for higher voltages. http://www.ti.com/lit/ds/symlink/cd40109b-q1.pdf |
| theatrical scene:
--- Quote from: FrankBuss on January 22, 2019, 09:51:49 am --- --- Quote from: theatrical scene on January 22, 2019, 02:22:58 am --- --- Quote from: oPossum on January 22, 2019, 02:17:18 am --- --- Quote from: theatrical scene on January 22, 2019, 02:06:23 am --- The RPi has uses both inputs and outputs which means I would need to get both the 74HCT and 74AHC parts right (for low-high level shifting and high-low)? --- End quote --- Yes. Forgot to mention the 74xxx541. That has a pinout that can be easier to work with than the 74xxx244. --- End quote --- Thanks, is there a version of this (or similar part) with 6-8 buffers built into a single package? --- End quote --- 74LVC8T245 has 8 buffers, and one pin to decide the direction control, which you can just tie to VCC(A) or GND for a fixed direction. --- End quote --- That looks very cool! I like the ability to control the DIR pin. Out of interest, is there a reason why I might use http://www.ti.com/lit/ds/symlink/txb0108.pdf over a 74LVC8T245 or is the TXB more useful in a bidirectional application? |
| Doctorandus_P:
Those TXB0108 are sort of overkill, but you can use them all the same. Ali / Ebay / China sells breakout boards with them, and the price and size of these breakout boards is about the same as a postage stamp. Often you can also use the good old 74LSxxxx logic as level converters. Those old transistor outputs can not deliver much current if the output gets above 3V3 |
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