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levelshift.html
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<!doctype html>
<html>
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<meta charset="utf-8">
<title>LEVEL SHIFTER | SHIENLONG</title>
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<link rel="stylesheet" href="style.css">
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<body>
<h1><a href="index.html">SHIENLONG</a></h1>
<hr>
<h2>LEVEL SHIFTER - TXB0108</h2>
<p>
I have a 3.3V digital output coming from the <a href="ft2232h.html">DLP-2232H</a> and at the other end, the device either accepts 1.2V or 1.8V but not 3.3V.
The <a href="https://www.ti.com/lit/ds/symlink/txb0108.pdf">TXB0108</a> level shifter accepts a wide range of voltages and is bidirectional, meaning it can take a 3.3V signal and translate it to a lower voltage or the other way around depending on your application.
<p>
It has 8-bits or 8 channels for your voltage translation. I only needed 4 but the additional pins are there should I need them for later expansion.
There is a OE (Output Enable) pin which is supplied by VCCA, meaning if you want the outputs turned on, set it to VCCA, otherwise just drive it low.
<p>
The VCCA and VCCB pins require a 0.1uF ceramic bypass capacitors. It is a pretty straightforward setup.
A 50kOhm resistor is required if pull-up/pull-down is required.
<p>
I tested it with a cheap sample from Shopee. Once I have determined it is working with my application on the breadboard, I purchased the parts from <a href="https://element14.com/">Element14</a>.
<p>
I had drawn a schematic and layout using KiCAD.
The available part package from Element14 was a WSON package type.
I had never hand soldered this package type before.
However, it was not too difficult.
It is possible to solder it using 1mm solder and 1mm bend conical tip.
However, maybe a smaller, less than 1mm sized tip and solder wire would have worked better.
I had several boards to solder, the heatgun method worked as well.
<p>
Update 26/08/2023 -
One of the boards soldered using the heatgun method had a problematic pin. I had to touch up with solder every time there is an issue.
I suspect the problem to be the materials and methods I used.
I did not have fresh solder paste, so instead I added solder to the pads along with some flux.
Then placed the level shifter on the pads and used the heatgun to melt the solder.
<p>
Another board soldered using 1mm solder tip did not have such issue.
I might try again on a spare board if I have fresh solder paste.
<p>
Another update is related to the VCCB voltage.
Previously I tested a situation where VCCB is equal to VCCA and was still able to run my application.
However, my application ran into issues after a few days of testing.
My tests run for several hours, so it was quite a surprise that a new issue surfaced.
<p>
The level shifter seems to be drawing current from another supply.
This issue disappeared once I increased the VCCB supply (relative to VCCA).
</p>
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