7400 Series Guide: 74HC48/74LS48 (BCD to 7-segment)

The 74×48 (ex 74LS48) is a chip designed as a BCD (Binary-Coded Decimal) to 7-segment display decoder. It is used to convert binary coded decimal input into the control signals needed to drive a typical 7-segment LED display, which can be useful in creating digital readouts from binary data.

In this guide, you’ll learn the things you need to know about this chip in order to use BCD to 7-segment display decoding in your own projects.

What does the 74HC48 / 74LS48 do?

The 74×48 is a BCD (Binary-Coded Decimal) to 7-segment display decoder. It takes a 4-bit BCD input and converts it into signals that can drive a 7-segment display to show the corresponding decimal digit from 0 to 9.

Each segment of the display is controlled by an output pin on the 74×48. The chip generates the correct combination of outputs to light up the appropriate segments for each digit. It also includes features like ripple blanking, which helps manage leading zeros, and an input that you can use to manually blank the display.

This makes the 74×48 very handy when you want to display numbers using 7-segment displays in digital clocks, counters, or other numeric displays.

How To Use This Chip

The 74LS48 comes in a 16-pin package, and you need to connect its power pins 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 74HC48 supports 2V to 6V, while the 74LS48 only supports 5V.

This chip uses open-collector outputs in combination with internal pull-up resistors, like this:

This means you can connect your 7-segment display directly to the outputs, without using external resistors, which is very practical, especially for simple test circuits.

74LS48 Pinout

The 74×48 has 16 pins and contains BCD to 7-segment (common cathode) decoder/driver with open-collector outputs laid out as shown in the pinout diagram below:

Pin Name	Pin #	Type	Description
B	1	Input	BCD input bit 1.
C	2	Input	BCD input bit 2.
LT	3	Input	Lamp test input (active low).
RBO/BI	4	Input	Ripple blanking output / Blanking Input (active low).
RBI	5	Output	Ripple blanking input (active low).
D	6	Input	BCD input bit 3.
A	7	Input	BCD input bit 0.
GND	8	Power	Connect to ground (GND).
e	9	Output	Output to segment e of the 7-segment display.
d	10	Output	Output to segment d of the 7-segment display.
c	11	Output	Output to segment c of the 7-segment display.
b	12	Output	Output to segment b of the 7-segment display.
a	13	Output	Output to segment a of the 7-segment display.
g	14	Output	Output to segment g of the 7-segment display.
f	15	Output	Output to segment f of the 7-segment display.
VCC	16	Power	Positive power supply. Connect to +5V power.

Alternatives and Equivalents for 74HC48 / 74LS48

There are many versions of the 74×48 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:

• 74HC48 (High-speed CMOS)
• 74HCT48 (High-speed CMOS, TTL compatible)
• 74LS48 (High-speed TTL)
• 74LVC48 (Low Voltage TTL)
• 74AC48 (Advanced CMOS)
• 74ALS48 (Advanced Low-Power Schottky TTL)
• 74F48 (Very High Speed)
• 74C48 (CMOS, similar to the 4000-series)

Some manufacturers also add a prefix, such as the SN74HC48 and SN74LS48 by Texas Instruments.

Can’t find the 74×48 anywhere? Then try one of the following IC alternatives:

• 74×247 – BCD to 7-segment decoder/driver (with open-collector outputs).
• 74×47 – BCD to 7-segment decoder/driver with active low outputs.
• 74×49 – BCD to 7-segment decoder/driver.
• CD4511 – BCD to 7-segment latch/decoder/driver.

If you can’t find the 74×48 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 74LS48 and 74HC48 chips

Download the PDF datasheet for your version of the 74×48 here:

• 74LS48 (Futurlec)
• SN74LS48 (Texas Instruments)