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Below you will find a link to the datasheet for 74HC4050N. My order I placed had a suffix of ",652" on that part, but I'm not sure what that number refers to.

http://www.nxp.com/documents/data_sheet/74HC4050_CNV.pdf

I'm trying to level shift a 5V data input to 3.3V output with this component. Most level shifters that I've found in the past have two VCC pins. One for each specific voltage. This looks like the VCC pin will take -0.5V to +7V. So I'm not sure what voltage I should connect. The -0.5V confused me.

Also, the A pins and Y pins have a Low and a High, I think. So I'm not sure how those should be used either, and what pins signifies an actual channel.

Here's ultimately what I'm after:

I have my Arduino with a TX pin and Rx pin. Then I have a module needing 3.3V and has TX and RX pins as well. However, I read that I need to level shift these two pins since the Arduino is 5V, and doesn't match the module (3.3V).

PS: I'm not an electrical engineer, so this may sound trivial.

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  • \$\begingroup\$ Regarding the VCC pin, -0.5 V - 7 V is an absolute maximum ratings, if you stay between these values, the IC will not be harmed your IC. Also if you scroll further below, there are the recommended conditions for VCC which is 2 V - 6 V. \$\endgroup\$ May 26, 2016 at 7:44

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The chip you selected can take a supply voltage input (vcc) from -0.5 to 7V; providing such a supply will guarantee that you will not damage the chip. However the recomended voltage range for Vcc is from 2 to 6v, therefore you should work within this range.

The voltage level of the output signal from the chip will depend on the value of VCC. So the output signals (Y) will be High or low depending on the inputs (A) but their magnitude is dependent on VCC.

You can see how much the output (y) will be from the first section of page 6 on the datasheet. You basically need to use a VCC of 3.3V.

SO connect VCC to 3.3V connect A1 to arduino and y1 to other (3.3v) device.

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  • \$\begingroup\$ So should I use this level shifter (74HC4050N) for Arduino Tx (5V) to module Rx (3.3V) so I don't fry the ESP module? And just connect the ESP module Tx directly to Arduino Rx, without level shifting? I got all confused when I found a UART web page that said UART Tx goes to ESP module Tx, and UART Rx goes to ESP module Rx. But when coming from Arduino, Arduino Tx goes to ESP Rx, and ESP module Tx goes to Arduino Rx. Maybe it was a typo? \$\endgroup\$ May 26, 2016 at 9:04
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    \$\begingroup\$ Yes thats right. This would work since arduino recognises any voltage above 3V as HIGH source, so connecting a 3.3v signal to it is fine. With regards to TX and RX its all relative; your module could have been labelled so that its easy to use and enables you to connect a tx to a tx and rx to a rx. If the guide says that you should do that. However, the actual way to understand this is that a transmitter(TX) would be connected to a receiver(RX). When trying out just check the voltage levels are correct and swap pins if it doenst work. \$\endgroup\$
    – Adam Z
    May 26, 2016 at 9:14
  • \$\begingroup\$ I'll test this out later and see how it goes. \$\endgroup\$ May 26, 2016 at 18:28

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