Logic Inverter Gates reverse the logic level: when inputting a high signal, they output low, and vice versa.
Since logic inverter gates are often also capable of sourcing and sinking considerable currents, they can be used to add additional GPIOs that reverse hthe behavior of existing GPIOs: if i.e. you need to open one relais and at the same time close another relais, instead of using two GPIOs, you could use just one, and drive the second relais with a logic inverter gate chip.
SN74LVC1G04 from Texas Instruments
The SN74LVC1G04 is a single inverter gate IC from Texas Instruments that’s cheap, easily available, and popular among DIY makers:
- Wide Voltage Level: its voltage level (1.65V-5.5V) supports both 3.3V and 5V microcontrollers. It uses input clamping diodes as protection from voltage spikes and over-voltage.
- Sinking And Sourcing: it can sink and source up to 32mA at 5V supply, and 24mA at 3.3V supply. That is sufficient to drive small LEDs and any other outputs that would normally be driven directly by a GPIO.
- Energy Efficient: LVC (low voltage CMOS) has a low power consumption and supports fast operation.
Unfortunately, this chip is not available in through-pin DIP packages. The two largest packages are both designed for surface mount and require soldering skills when wiring them individually:
| Chip Model | Package |
|---|---|
| SN74LVC1G04DBV | SOT-23 |
| SN74LVC1G04DCK | SC-70 |
These IC are typically distributed as a reel (adding an R to the chip model number).
The SMB chips are tiny. Here is a side-by-side comparison with a 5mm LED and a SN74LVC1G04DCKR chip:
When enlarging the SN74LVC1G04DCKR, you can see the five pins that would need to be soldered to wires when using these chips in manually-soldered circuits:
Legit And Fake Chips
When enlarging the picture (or using a magnifying glass), you see the chip markings. The picture shows two SN74LVC1G04DCKR from different sources side by side: the left one came from an untrusted vendor at the AliExpress market place, and the right one was ordered by a renown distributor (Mouser).
Both markings look similar at most. They are different. Whether or not the dye inside the package is the same must be determined by a test.
Be aware there is a huge market for fake IC. When ordering from untrusted sources, you may get chips that (a) work pretty much like the original (well-made clones), (b) in tests work as expected but with real loads and specs, fail (clones that use lower quality dyes with lower maximum specs), (c) are in reality a lower-quality model (with lower specs), i.e. inverters that can sink and source much less current than the original, or MosFET that should be able to handle 30A but burn up at 5A, or (c) these chips were sorted out elsewhere and don’t work at all, or show unexpected behavior. With untrusted sources, you aren’t actually saving terribly much money compared to trusted distributors (just buy a certain minimum quantity and have your order exceed €50 to qualify you for free shipping). The worst issue with fake components is that they mess up your curcuit, and you waste hours and days to find errors that simply do not exist - in reality, your circuit failed because the components weren’t the ones you thought they were.
Pin-Out
All package types come with five pins:
Prototype Board
Since these inverter IC are tiny and supposed to be surface-mounted on a PCB, you would have to either produce your own PCB, or use PCB Adapter plates. These come in many different formats and designs.
Try and get one that matches exactly the package size of your chips. The SN74LVC1G04DCK i.e. uses a SC-70 package size.
Most commercially available PCP Adapters come in dual designs to support more package sizes. SC-70-compatible boards with six header pins and a 0.65mm pin spacing on one side often feature a SOT23 layout with 0.95mm spacing on the flip side.
Dedicated SC-70 PCB adapters aren’t as available as other formats, and that is also why they can be relatively expensive. SOP8-compatible eight pin PCB with a 1.27mm spacing on one side and a 0.65mm spacing on the other side may also work for SC-70 since the pitch (pin spacing) is what matters most.
If you use adapters that aren’t specifically made for SC-70 (but have a 0.65mm pitch), they may have more pins than you need (just leave some unconnected), and the chip size may not match exactly. Most likely, SC-70 chips are more narrow, so you may have to bridge some pin distance with solder.
As you see, while the 0.65mm pitch matches SC-70 perfectly, there are eight instead of six solder pads, and the SC-70 chip is too narrow for all of its pins to touch the solder pads on both sides:
Materials
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(content created Sep 04, 2024 - last updated Sep 06, 2024)