74HC238PW-Q100J

Logic - Signal Switches, Multiplexers, Decoders are essential components used in advanced applications or circuit designs. Each of these components plays a specific role in allowing certain data or signals to be routed to the appropriate output. 74HC238PW-Q100J from ON Semiconductor is a 3-to-8 line digital decoder/demultiplexer which is capable of decoding three bits of information into one of eight mutually exclusive outputs active-low.

The main application field of 74HC238PW-Q100J is interface control. With 3Inputs(A0, A1 and A2) and 8 Outputs(Y0, Y1, Y2, …….Y7), this decoder can be used to extend the number of outputs with only 3 inputs. For example, in a programmable keypad, this decoder can convert the single row address (A0, A1 and A2) to 8 outputs (Y0, Y1, Y2…..Y7) corresponding to each row of the keypad. Furthermore, if the keypad is a 3x3 matrix, then three 74HC238’s can be cascaded to control the logic of the individual keys.

The working principle of 74HC238PW-Q100J is based on its internal architecture. It has 3 Inputs, 8 output, 6 Active Low Enable Inputs(B0, B1, B2, #E0, #E1 and #E2) and two Active High Enable Inputs(#E1A and #E2A). The 3 inputs will be fed by an external source to the decoder that specifies which output is to be activated (Low). The Enable Inputs decide which 3 bits are to be decoded. When the Enable Inputs are active, the decoder will decode the Inputs and generate the corresponding output.

The working of 74HC238PW-Q100J is as follows. If the #E0, #E1, #E2 inputs are active then the 3 inputs (A0, A1, A2) will be decoded and active low output(Y0, Y1, Y2…..Y7) will be generated. If #E1A and #E2A are active, then the above mentioned 3 inputs will be decoded in pairs (A0 and A1, A2 and A0, A1 and A2). The output will be ‘1’ for the pair (A0 and A1, A2 and A0, A1 and A2) and the remaining output will be ‘0’.

Another application of the 74HC238PW-Q100J decoder is for a 3x3 8 key matrix for controlling a logic circuit. The logic circuit can be a calculator (for example) that operates with 8 keys. In this application, the logic circuit will send out three signals (A0, A1 and A2) to indicate which row of the key matrix has been pressed. The 74HC238PW-Q100J will receive the three signals, decode them and output the corresponding signal to the logic circuit. The signal will be the column address of the particular key pressed.

The 74HC238PW-Q100J decoder can also be used with five output logic circuits. In this case, the A0, A1 and A2 inputs will be used to determine the output state of the logic circuit. The other two inputs (#E1A, #E2A) will enable or disable each output. When the enable inputs (#E1A, #E2A) are active, the output of the decoder will be determined by the A0, A1 and A2 inputs, otherwise it will be 0.

The 74HC238PW-Q100J decoder can be used in many applications controlling multiple outputs from a single input source. It can be cascaded with other circuit elements to control the logic of a particular circuit. As it is a digital device, it is also suitable for use in low voltage systems and provides a reliable and accurate output.