LED display repair starter chip of 74HC138D

LED display repair starter chip of 74HC138D

Overview: 74HC138D is a three-channel input, eight-channel output decoder , mainly used in consumer electronics. In the display, 138 input ABC signal, output Y0 to Y7 into four MOS driver tube 4953. 

Main features.

1, using CMOS process

2, low power consumption

3, operating voltage: 3.0V-5.0V 

4, Package form: SOP16

Features and benefits

Input levels:

For 74HC138: CMOS level

For 74HCT138: TTL level

Demultiplexing capability

Multiple input enable for easy expansion

Ideal for memory chip select decoding

Active LOW mutually exclusive outputs

ESD protection:

HBM JESD22-A114F exceeds 2000 V

MM JESD22-A115-A exceeds 200 V

Multiple package options

Specified from -40 °C to +85 °C and from -40 °C to +125 °C

Friends who have not studied electronics or binary must be very difficult to read! This information is only to the application level as well as maintenance personnel to provide reference, the implementation of specific functions, a basic friend can go to check the manufacturer's data.74HC138D datasheet。

Write it differently: E3 is the core that determines whether the chip works or not. Only when E3 is normal and low, the chip can output normally. 3-8 decoder, that is, the input is binary, the output decimal.

For example: input A2A1A0 for 000, decimal output 00000001, here after taking the inverse 111111110.

          input A2A1A0 for 001, decimal output 00000010, here after taking the inverse 111111101.

    And so on! Why take the inverse, please check the manufacturer's data for details.74HC138D datasheet。

Actual led display maintenance case analysis: If the unit board has 2 lines do not light up when the line and line is a multiple of 8, you can check the output of 138 or 4953 whether it is working properly.