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Topic: Shift Register Output Voltage (Read 787 times) previous topic - next topic

TheGrovesY

A Quick question. Is the voltage of the output pins on a shift register the same and you put in on the Vcc?

Thanks

retrolefty


A Quick question. Is the voltage of the output pins on a shift register the same and you put in on the Vcc?

Thanks


In almost all cases, yes that is true. There are however some special shift register chips that have special output pins that have constant current active low output pins for driving things like LEDs.

Lefty


Onions

http://datasheet.octopart.com/M74HC595B1R-STMicroelectronics-datasheet-5318008.pdf

The datasheet (page 4) says the maximum input voltage is 7v (for the 74HC595), so, adding to what lefty said, the voltage output will be the same as the input voltage. If the input voltage is more than 7 volts thugh, the output will soon go down to 0v :D .

Onions.
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TheGrovesY


James C4S

Note that this answer applies specifically to the 74HC595.  It is likely this is the shift register you have and it is likely the advice given is true.  However, without knowing the exact part number you are working with, your question cannot be answered. 
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TheGrovesY

Yeah that makes sense and looking at the datasheet thats what it implied but wanted to check i understood correctly.

Thanks again. I'm starting my first real project, so will almost certainly be asking more questions  XD

MarkT

Its a 74HC series logic chip, it behaves like all the other 74HC logic chips - its CMOS so the output is either 0V or Vdd (or if overloaded somewhere inbetween)

The recommended maximum supply is 6V.  7V is an absolute max rating, avoid it.

I'm not sure if someone is confusing 'input' with 'supply'.  The shift register does not shift a voltage level, it shifts a logic state (LOW or HIGH). It specifically is not an analog bucket brigade delay line chip...
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