7400 Series Guide: 74HC239/74LS239 (Dual 1-of-4 decoder)

The 74×239 (ex 74HC239) is a chip that features two sets of 2-to-4 line decoders with address latches.

In this guide, you’ll learn the things you need to know about this chip in order to use address decoding and latching in your own projects.

What does the 74HC239 / 74LS239 do?

A 2-to-4 line decoder/demultiplexer is a digital circuit that takes in a 2-bit signals and turns on one of its four outputs.

The primary function of such a decoder is to convert binary coded information into a form that can drive one of several outputs, activating only one at a time. This is useful in applications like enabling one of several devices or channels.

Each decoder has:

• Four data outputs (Y0 to Y3).
• Two data inputs (S0 and S1) to choose which of the four inputs to turn on.
• An enable input to control if the multiplexer is active (EN).

Multiplexers like the 74×239 are useful for routing data in circuits, allowing a shared connection point to switch between different data lines.

How To Use This Chip

The 74HC239 comes in a 16-pin package, and you need to connect it to power before you can use it. Most 7400 ICs support a VCC voltage of 5V. One difference between the HC and LS version of the chip is that the 74HC239 supports 2V to 6V, while the 74LS239 only supports 5V.

74HC chips can normally supply a maximum of 4 mA from an output pin. If you’re using the 74LS version, the maximum current you can pull out of one output pin is 0.4 mA when the pin is high (sourcing) or 8 mA when the pin is low (sinking).

But these values can differ between models, so check the datasheet of your model to verify.

Once you’ve connected it to power, you can use the Decoder/Demultiplexer inside.

74×239 Pinout

The 74×239 has 16 pins and contains two 1-of-4 noninverting decoder/demultiplexer laid out as shown in the pinout diagram below:

Pin Name	Pin #	Type	Description
1EN	1	Input	Enable input for the first Decoder/Demultiplexer (active low).
1S0	2	Input	Select line 0 for the first Decoder/Demultiplexer.
1S1	3	Input	Select line 1 for the first Decoder/Demultiplexer.
1Y0	4	Output	Output 0 from the first Decoder/Demultiplexer.
1Y1	5	Output	Output 1 from the first Decoder/Demultiplexer.
1Y2	6	Output	Output 2 from the first Decoder/Demultiplexer.
1Y3	7	Output	Output 3 from the first Decoder/Demultiplexer.
GND	8	Power	Connect to ground (GND).
2Y3	9	Output	Output 3 from the second Decoder/Demultiplexer.
2Y2	10	Output	Output 2 from the second Decoder/Demultiplexer.
2Y1	11	Output	Output 1 from the second Decoder/Demultiplexer.
2Y0	12	Output	Output 0 from the second Decoder/Demultiplexer.
2S1	13	Input	Select line 1 for the second Decoder/Demultiplexer.
2S0	14	Input	Select line 0 for the second Decoder/Demultiplexer.
2EN	15	Input	Enable input for the second Decoder/Demultiplexer (active low).
VCC	16	Power	Positive power supply. Connect to +5V power.

Alternatives and Equivalents for 74HC239 / 74LS239

There are many versions of the 74×239 chip. They all have the same functionality, but with different specifications such as supported voltages and maximum current output.

Here’s a list of a few equivalents of this chip:

• 74HC239 (High-speed CMOS)
• 74HCT239 (High-speed CMOS, TTL compatible)
• 74LS239 (High-speed TTL)
• 74LVC239 (Low Voltage TTL)
• 74AC239 (Advanced CMOS)
• 74ALS239 (Advanced Low-Power Schottky TTL)
• 74F239 (Very High Speed)
• 74C239 (CMOS, similar to the 4000-series)

Some manufacturers also add a prefix, such as the SN74HC239 and SN74LS239 by Texas Instruments.

Can’t find the 74×239 anywhere? Then try one of the following IC alternatives:

• 74×137 – 3-to-8 line decoder/demultiplexer.
• 74×138 – 3-to-8 line decoder/demultiplexer.
• 74×139 – Dual 2-to-4 line decoder/demultiplexer.
• 74×154 – 4-to-16 line decoder/demultiplexer.
• 74×155 – Dual 2-to-4 line decoder/demultiplexer.
• 74×237 – 3-to-8 line decoder/demultiplexer.
• 74×238 – 3-to-8 line decoder/demultiplexer.
• CD4514 – 4-to-16 line decoder with latched inputs.
• CD4515 – 4-to-16 line decoder with latched inputs.
• CD4555 – Dual 1-to-4 line decoder/demultiplexer.
• CD4556 – Dual 1-to-4 line decoder/demultiplexer.

If you can’t find the 74×239 IC in your local electronics store, don’t worry, you’ll most likely find it in one of the stores listed on this page of online stores where you’ll find components and tools for all your electronics projects.

Datasheet for the 74LS239 and 74HC239 chips

Download the PDF datasheet for your version of the 74×239 here:

• 74HC239 (Rochester Electronics)
• SN74HC239 (Texas Instruments)