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Changing decade counter IC's output

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So, i built a circuit in real life with a 74ls390 and its output follows the voltage of the Vcc but when I build the same circuit on multisim, the output is always 5V regardless of Vcc voltage.

Screenshot 2022-05-13 190545.jpg

i am hoping that there are some settings that can be changed to change the output voltage of the output pins or some other decade counter IC that would change their output voltage according to Vcc of the circuit.

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Accepted by topic author johndoeeerae

Привет, дорогой!
Идеальная модель в программе предполагает 5 вольт. Так задумали разработчики. Переключив на реальную в смешанном моделировании, теряем скорость, но получаем более реальные результаты.

VCC.gif

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why is it outputting negative voltage

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In case you need my testing circuit:

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Обратите внимание на "землю". Нужно выставить цифровую

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Во вкладке "состав модели" есть таблица выводов, куда какое питание подключать.

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ahhhhh i see, thank you very much

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"Спасибо" в карман не положишь, а звезда хоть правильный путь укажет в нашем грешном мире 😀
Спасибо вам за оценку!

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Hi johndoeeerae and tipa,

 

 

The logic family 74LSxxx (Low-Power Schottky) is designed for 5 V digital circuits. The absolute maximum rating for its power supply voltage is only 7 V while the recommended operating condition is Vcc = 5 V ±5% for a range of 4.75 V to 5.25 V. You are attempting to use a 9 V supply voltage for the IC and it may appear that your experiment is successful in simulation. On the other hand, if you will build the real circuit, the excessive supply voltage is very likely to cause damage to the IC.


Here are some of my recommendations so you might be able to achieve your objective:

 

  •  You can slightly raise the power supply voltage up to 6 V if you will use the CMOS 74HC390. For its Supply Voltage (Vcc/Vdd) the Absolute Maximum Rating is -0.5 V to +7.0 V and the Recommended Operating Condition is 2.0 V to 6.0 V.
  • The 74xx390 is a Dual 4-Bit Decade Counter. It seems, however, that you only want to experiment with only one section/counter of the IC. If you are not satisfied with 6 V using the 74HC390 you can use the CD4029 Presettable Binary/Decade Up/Down Counter. The CD4029 has a wide supply voltage range, 3V to 12V for CD4029A, 3V to 15V for CD4029B, (maybe) even higher depending on the manufacturer, but the IC contains only a single counter.
  • If you really need a dual counter with wide power supply voltage range you can opt for CD4518 Dual BCD Synchronous Up Counter. The CD4518 has a wide supply voltage range like the CD4029 but the latter can only count up.

The counters CD4029 and CD4518 are both synchronous while the 74xx390 is a ripple counter (please verify this from the datasheets to be sure). However, this difference may not be important in what you are doing.

 

 

 

Best regards,
G. Goodwin

 

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Спасибо за уточнения!

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