7400 Series Guide: 74HC237/74LS237 (3-to-8 line decoder)

The 74×237 (ex 74HC237) is a chip that contains a 3-to-8 line decoder/demultiplexer with address latches and an enable input.

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

What does the 74HC237 / 74LS237 do?

The 74×237 is a 3-to-8 line decoder with an added bonus: it has three state outputs.

Here’s how it works:

• It takes in three binary inputs and decodes them to control up to one of eight outputs. So, depending on the input combination, one specific output will go LOW, while all others stay HIGH.
• It includes a “latch enable” (LE) input, ensuring the decoder is active only when this input is HIGH.
• The outputs are three-state, meaning they can be in one of three conditions: HIGH, LOW, or high-impedance (i.e., disconnected).

This decoder is useful when you need to control multiple outputs from a few input lines, such as in address decoding in memory circuits.

How To Use This Chip

The 74HC237 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 74HC237 supports 2V to 6V, while the 74LS237 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.

74×237 Pinout

The 74×237 has 16 pins and contains 1-of-8 noninverting decoder/demultiplexer with address latches laid out as shown in the pinout diagram below:

Pin Name	Pin #	Type	Description
S0	1	Input	Select input bit 0 for the Decoder/Demultiplexer.
S1	2	Input	Select input bit 1 for the Decoder/Demultiplexer.
S2	3	Input	Select input bit 2 for the Decoder/Demultiplexer.
LE	4	Input	Latch Enable (active low), enables the latching of address inputs.
EN2	5	Input	Enable input 2 (active low) for enabling the device.
EN1	6	Input	Enable input 1 for enabling the device.
Y7	7	Output	Output line 7 from the Decoder/Demultiplexer.
GND	8	Power	Connect to ground (GND).
Y6	9	Output	Output line 6 from the Decoder/Demultiplexer.
Y5	10	Output	Output line 5 from the Decoder/Demultiplexer.
Y4	11	Output	Output line 4 from the Decoder/Demultiplexer.
Y3	12	Output	Output line 3 from the Decoder/Demultiplexer.
Y2	13	Output	Output line 2 from the Decoder/Demultiplexer.
Y1	14	Output	Output line 1 from the Decoder/Demultiplexer.
Y0	15	Output	Output line 0 from the Decoder/Demultiplexer.
VCC	16	Power	Positive power supply. Connect to +5V power.

Alternatives and Equivalents for 74HC237 / 74LS237

There are many versions of the 74×237 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:

• 74HC237 (High-speed CMOS)
• 74HCT237 (High-speed CMOS, TTL compatible)
• 74LS237 (High-speed TTL)
• 74LVC237 (Low Voltage TTL)
• 74AC237 (Advanced CMOS)
• 74ALS237 (Advanced Low-Power Schottky TTL)
• 74F237 (Very High Speed)
• 74C237 (CMOS, similar to the 4000-series)

Some manufacturers also add a prefix, such as the SN74HC237 and SN74LS237 by Texas Instruments.

Can’t find the 74×237 anywhere? Then try one of the following IC alternatives:

• 74×138 – 3-to-8 line decoder/demultiplexer.
• 74×139 – Dual 2-to-4 line decoder/demultiplexer.
• 74×238 – 3-to-8 line decoder/demultiplexer.
• CD4028 – BCD to decimal/hexadecimal decoder.
• CD4514 – 4-to-16 line decoder/demultiplexer with latched inputs.
• CD4515 – 4-to-16 line decoder/demultiplexer with latched inputs.

If you can’t find the 74×237 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 74LS237 and 74HC237 chips

Download the PDF datasheet for your version of the 74×237 here:

• 74HC237 (Futurlec)
• 74HC237 (Nexperia)
• TC74HC237 (Toshiba)