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SN74HC164: SN74HC164 output issue

user5959647
Intellectual 960 points
Part Number: SN74HC164

1.VDDH=3.3V, When connecting with the first four LEDS, the output of LED0~LED4 is normal, but connecting with LED5 and LED6, the LED0~LED4 turn off and SN74HC164 has no output voltage (Q0~Q3)

2.Even connected LED1and LED2 can be work normally ，When LED5,LED6 or LED7,LED8 are connected, the previous LEDs will also be off and the I/O pin has no voltage output.

3. The project has already been mass-produced, Which parameters are causing this problem?

  • 0
    TI__Guru* 96947 points

    Hello,

    I don't see any obvious error from the shown schematic.

    Can you share oscilloscope shots of the CP and DSB pins of the two shift register devices? It would be helpful to see all 4 waveforms together on the same scope shot to compare timing. Preferably we can see 100ns or less time scale for each transition.

    It would also be helpful if I can see a photo of the board, just so I can understand better the layout and operation.

  • 0 in reply to Emrys Maier
    Intellectual 960 points

    I found that U10 LEDs are turn off and no output voltage if U11 LEDs connect.This problem was not found in mass production before, but the problem occurred this time. Which specification parameters would affect it, so I thought it was the insufficient driving current. However, this problem still exists when LED0 to LED1 is connected to LED5 to LED6 again.

  • 0 in reply to user5959647
    TI__Guru* 96947 points

    The time scale on this scope shot is huge - I cannot see the details I need. Can you look at 100ns/V or faster for clock and data inputs?