Overview of 5 to 32 Decoder ICs

A 5 to 32 decoder IC takes a 5-bit binary input and decodes it into a 1-of-32 output. This allows the 5-bit input to uniquely select one of 32 output lines. Decoder ICs like this are useful in many digital logic applications where a binary input needs to be converted into a set of control or select lines.

Some key features of 5 to 32 decoder ICs:

• Input is 5 bits wide
• 32 output lines
• Only one output line is active (high) at a time
• Output lines are active low by default (can also get active high variants)
• Enable input to enable or disable all outputs
• Output can source or sink current up to several mA per line

Popular Chips

Some popular chips with 5 to 32 decoding capabilities:

74HC154

• Fast CMOS logic
• Active low outputs
• Output current of 24mA sink/source per output pin
• Propagation delay of 15ns

74HCT154

• CMOS logic with TTL-compatible input thresholds
• Active low outputs
• Output current of 20mA sink/source per output pin
• Propagation delay of 13ns

CD4532B

• Bipolar logic
• Active low outputs
• Output current of 16mA sink/source per output pin
• Propagation delay of 4.5ns

Applications

Some example applications of 5 to 32 decoder ICs:

• Driving individual digits in a 7-segment LED display
• Selecting 1 of 32 memory chips or I/O devices
• Generating timing and control signals in a circuit
• Implementing logic functions and small state machines

Here is a simple example circuit using a 5 to 32 decoder to drive a 7-segment display:

The BCD data is latched into the decoder on each clock cycle, and the decoder drives the appropriate segments to display the number. The decoder acts as a BCD-to-7-segment converter.

FAQ

What is the main difference between decoder and encoder ICs?

An encoder takes multiple input lines and encodes them into a more compact binary output code. A decoder does the reverse: it takes a compact binary input code and decodes it into a set of output lines.

How do I choose the right decoder IC for my application?

Consider the number of inputs/outputs needed, the logic family (CMOS, TTL, etc.), output drive current, propagation delays, power supply levels, and other parameters. Make sure the decoder is compatible with the rest of your circuit.

Can I cascade multiple decoder ICs to decode more than 32 lines?

Yes, decoder outputs can be fed into the inputs of subsequent decoders to scale up. For example, two 5-to-32 decoders chained together could provide 32*32=1024 output combinations.

What is an active low vs. active high output on a decoder?

Active low means the output line goes low when selected. Active high means the output goes high when selected. Some decoders have both options. Using the active option that matches the rest of your circuit logic avoids extra inverters.

How do I enable or disable all outputs on a decoder IC?

Many decoders have an Enable or Output Enable pin. Setting this low disables all outputs for a high-impedance tri-state condition. Setting it high enables the outputs. This allows easily controlling all outputs at once.CopyRetry