Electronics > Beginners
Level Shifting: practical differences between these two components
vmallet:
I'm exploring the world of level shifting to interface 5v systems with 3.3v or vice versa, and I'm wondering what the practical differences are between these two components:
* TI TXS0108E8-Bit Bi-directional, Level-Shifting, Voltage Translator: http://www.ti.com/lit/ds/symlink/txs0108e.pdf
* TI SN74LVC2T45 Dual-Bit Dual-Supply Bus Transceiver With Configurable Voltage Translation: http://www.ti.com/lit/ds/symlink/sn74lvc2t45.pdfI can read the datasheets and see some differences but I'm lacking the basic knowledge of why would one use one vs. the other depending on applications. What are the fundamental differences?
Could someone shed some light?
ataradov:
The major difference is that SN74LVC2T45 is not bi-directional. There is a DIR input that controls which side is input and which side is output.
TXS0108E8 is automatic. You put it between the rails and it does the shifting.
vmallet:
--- Quote from: ataradov on January 09, 2020, 07:23:21 am ---The major difference is that SN74LVC2T45 is not bi-directional. There is a DIR input that controls which side is input and which side is output.
TXS0108E8 is automatic. You put it between the rails and it does the shifting.
--- End quote ---
Thanks Alex. So in that case, why would one chose to use the SN74LVC2T45 when the TXS0108E8 does everything on its own? Is it a bandwidth difference?
T3sl4co1l:
The "automatic" parts are notorious for glitching. The traditional directional bus driver is used when you have the requisite bus control signals available and require provable and repeatable functionality.
Tim
ataradov:
--- Quote from: vmallet on January 09, 2020, 05:40:11 pm ---Thanks Alex. So in that case, why would one chose to use the SN74LVC2T45 when the TXS0108E8 does everything on its own? Is it a bandwidth difference?
--- End quote ---
Their architecture matters a lot. SN74LVC2T45 has a real push-pull output, so it also acts as a buffer for the signals.
TXS0108E8 does not really buffer the signals. It essentially does what a typical MOSFET-based level shifier does.
I assume price is also a factor, but I can't even find the price for TXS0108E8.
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