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CD4504B: CD4504BPW (CM504B) F in/out not working properly.

Josep Soler
Prodigy 30 points
Part Number: CD4504B

Hello,

As previously posted and deleted, I did ask if F in/out was special or had some other functions and the answer was no.

Now I'm tstill rying to fix an issue with F input/output on CD4505B where F out can't get at 0V when F in is at 0V . 

I do have the following connections:

1- 

2-

Description of the issue:

When connecting a NO push button on input 13 and 14 to GND, Fin and A in signals are 5V from the pull-up, when pushing the button both inputs go down to 0V and output also goes down to 0 V. However, when the push button is not connected directly, using a cable (more than 30cm), F in  (In13 signal)  goes down to 0V but F out goes down to 4.5V instead of 0 V.  But if we do replicate the circuit on In14 (A in), the output (A out) goes down to 0 instead of the 4.5V we do get on F out. 

When transient testing, F gate does not work properly (neither In1 nor In13) .

On both cases, it gets up to 200ºC after a few seconds .

On the previous question i did post, I was told to put a Capacitor on Vcc and Vdd since F gate was the farthest gate from source. 

After modifying the circuit, results got worst, F out could not get under 4.8V when F in was 0V.

Also have tried to put a capacitor at the F in and A in (In13 & In14), but F gate seems more sensible and even with a 100n capacitor In13 (Fin) does not work and can't make F out 0V. 

According to data sheet, on CMOS-CMOS low lvl is under 1.5V and TTL-CMOS lov level is under 0.8V.

Notes:

  • Vin = 17V (16.8V).
  • All outputs are connected to a micro controller.
  • All inputs have a pull-down of 1M .
  • 5V input signals had been used on tests. (Input signals range from 0-3.5V to 0.16V).
  • Datasheet .
  • Inverted signals is not an issue, since i can swap them inside the micro controller.
  • All voltages are DC.
  • 0
    Guru 316690 points

    A decoupling capacitor is always necessary.

    The input switching thresholds depend on VCC. Voltages between VIL and VIH are invalid. You must connect VCC to 5 V. (Why is Vin so high, and why are you using a level shifter? Is there ever a voltage above 5 V?)

  • 0
    TI__Guru 50446 points

    Hi Josep, 

    I am not sure why it says deleted please see my previous follow up if any feedback, thanks.

    Best Regards,

    Michael.

  • 0 in reply to Clemens Ladisch
    Prodigy 30 points

    Hi Clemens,

    My fault, I see i did an error when posting the information.

    Input signals range from 0-3.5V to 0-16V

    instead of 

    Josep Soler said:
    5V input signals had been used on tests. (Input signals range from 0-3.5V to 0.16V).

    I assume now it makes sense to use a level shifter since in some cases same input will have 0-3.5 V or 0-9 V  or even 0 - 16V since i need one board to handle all cases without modifying the input signal, a level shifter fits quite well in there, so the micro controller will always get 0 - 5V .

    And also you can see i do have some input signals over  5V .

    Clemens Ladisch said:
    Voltages between VIL and VIH are invalid. You must connect VCC to 5 V.

    I don't think so, at least in this other post, where the question is 15V in to 5V out and asksk if the connections are right, the answer is yes. 

    So I just followed recommendations and the data sheet.

    Edit: Michael, thanks for pasting it! 

    I would say I do have swapped Vcc and Vdd, but as mentioned above, this level shifter, "shifts signals from the Vcc logic level to the Vdd logic level" so if Vcc = 5V and Vdd = 17V then i'd get 17V output instead of 5V output and the micro controller is 5V compatible but not 17V.

    When I do say Vin = 16.7 (17V) i do refer the Vin on the schematic, Vcc on the shifter.



    Related to the recommended operating conditions, Supply  means Vcc ? (5V in this case) and Voltage range is the high (3.5 - 16V value of the inputs signals), the overall input values ( 0 - 16V ) ot the Voltage range on Vcc (in this case 5V stable) ?

    And last point, The 1M pull-down are always active i can't disable them, and the pull up, on In13 (F in) and In14 (A in) are always active. In2 (A in) and In3 (B in)  do have and enable switch as shown in the schematic.

    Regards,

    Josep

  • 0 in reply to Josep Soler
    Guru 316690 points

    When VCC is 16.8 V, then the input signals (xIN, SELECT) must also be that high. But the inputs are overvoltage tolerant, so you can use VCC = 5 V with higher input signals.

  • 0 in reply to Clemens Ladisch
    Prodigy 30 points

    I had also connected select to 16.8V  as Vcc was 16.8V according to data sheet to have TTL to CMOS but still did had this issue with F in/out.

    Also with CMOS - CMOS configuration (Select = GND) I do have this issue.

  • 0 in reply to Josep Soler
    Guru 316690 points

    With 5 V input signals, you need a VCC of 5 V.

  • 0 in reply to Clemens Ladisch
    Prodigy 30 points

    Yes, i do agree, but  as you can see on my schematic, i may have 0-3.5V on A in  in some cases, while in other cases i'll get 0.5 or 0-8 or 0-16 so i can't assume i have 5V inputs. 

    Just to clarify a little the situation, the purpose is to have a generic boardso I can use it in different situations i'll put 3 different cases :

    Signal Pin Case 1 Case 2 Case 3
    In1 Fin 0-3,5V 0-8,7V 0-4,5V
    In2 Ain 0-16V 0-8,7V 0-4,5V
    In3 Bin 0-16V 0-8,7V 0-4,5V
    In4 Cin 0-3,5V 0-8,7V 0-4,5V
    In5 Din 0-3,5V -
    In6 Ein 0-3,5V 0-8,7V 0-4,5V
    In7 Cin 0-3,5V 0-8,7V -
    In8 Bin - 0-5V -
    In9 Din - 0-5V -
    In11 Ein 0-5V 0-8,7V 0-5V
    In13 Fin 0-5V 0-8,7V 0-5V
    In14 Ain 0-5V 0-8,7V 0-5V

    So sometimes one input does have one max value when in other cases is another value but all the inputs must go to the microcontroller that only admits 5V .

    That being said, after testing Vcc = Vdd = Select = 5V  with 100nF decoupling capacitors results remain unchanged, for A,B,C,D,E in, when a high signal applied, the respective output changes to 5V, and when a low signal is applied, the output changes to 0 V. 

    However, When Fin gets a high signal, Fout gets high , but when Fin gets a low input, Fout remains over 4.8V 

  • 0 in reply to Josep Soler
    TI__Guru 50446 points

    Hi Josep,

    The 5V isn't for inputs but for the Vcc pin. Your inputs can be higher than supply similar to [FAQ] Can the input voltage (Vi) to my logic device be higher than the supply voltage (Vcc)?.

    Also note that, in your schematic; all A,B,C,D,E inputs are directed into the device and the corresponding outputs directed out of the device. 

    However, the FOUT and FIN both seems to be going into the device. Could you help clarify and double check FOUT is not getting an input? Thanks.

    Best Regards,

    Michael.

  • 0 in reply to Michael Ikwuyum
    Prodigy 30 points

    Hi Michael,

    I tested the 5V in Vcc  but did not get a better result:

    Josep Soler said:

    That being said, after testing Vcc = Vdd = Select = 5V  with 100nF decoupling capacitors results remain unchanged, for A,B,C,D,E in, when a high signal applied, the respective output changes to 5V, and when a low signal is applied, the output changes to 0 V. 

    However, When Fin gets a high signal, Fout gets high , but when Fin gets a low input, Fout remains over 4.8V 

    Michael Ikwuyum said:

    Also note that, in your schematic; all A,B,C,D,E inputs are directed into the device and the corresponding outputs directed out of the device. 

    However, the FOUT and FIN both seems to be going into the device. Could you help clarify and double check FOUT is not getting an input? Thanks.

    Thanks for pointing this out, i did not realize, I'll fix it but that's only graphical.
    On the pcb it's just a path going from Fout straight to the micro controller input.

  • 0 in reply to Josep Soler
    TI__Guru 50446 points

    Hi Josep,

    If I understand correctly, you have Vcc as 5V, Vdd as 5V and Select as HIGH for TTL levels.

    However, when Fin gets a low input, Fout remains high.

    Per your clarifications for the PCB path with no indication of bus contention, could you help confirm the state of Fin is actually low while sending a low input (with select also low)?

    I suspect when the push button is not connected directly; the line is still being held high (pulled up to Vcc) while using the 30 cm cable, and not low.

    You may also replacing with a new device (due to damages) as it seemed VCC was above 5V at some point (for TTL to CMOS), thanks.

    Best Regards,

    Michael.

  • 0 in reply to Michael Ikwuyum
    Prodigy 30 points

    Hi Michael,

    Michael Ikwuyum said:

    If I understand correctly, you have Vcc as 5V, Vdd as 5V and Select as HIGH for TTL levels.

    However, when Fin gets a low input, Fout remains high.

    That is correct.

    Michael Ikwuyum said:
    Per your clarifications for the PCB path with no indication of bus contention, could you help confirm the state of Fin is actually low while sending a low input (with select also low)?

    Yes, even with 30cm cable, at F in i see low input with select high and select low.

    Michael Ikwuyum said:
    You may also replacing with a new device (due to damages) as it seemed VCC was above 5V at some point (for TTL to CMOS), thanks.

    This has also been done several times with no improvement. 

    Since i could not solve the issue, i just moved to CD74HC4050PWR that has the same package, accepts up to 16V input and seems to work fine. Even when undergoing transient test.

    Regards

  • 0 in reply to Josep Soler
    TI__Guru 50446 points

    Hi Josep,

    I am glad you found a solution.

    To help further understand, could you help double confirm if the same 30cm cable was used for Ain and Fin inputs and the Aout and Fout output lines are similar?

    Any saved waveforms will also help, thanks.

    Best Regards,

    Michael.

  • 0 in reply to Michael Ikwuyum
    Prodigy 30 points

    Hi Michael, 

    Michael Ikwuyum said:
    To help further understand, could you help double confirm if the same 30cm cable was used for Ain and Fin inputs and the Aout and Fout output lines are similar?

    I can confirm that same cable was used in all inputs when being tested.

    Regards

  • 0 in reply to Josep Soler
    TI__Guru 50446 points

    Hi Josep,

    That is unusual. Especially since we haven't had such complaints for specific IOs compared to others.

    I would have liked to take the time to help clarify the root cause but won't bug you much since a solution was found. 

    Will go ahead to close the thread for now, but will pay attention for similar future complaints, thanks!

    Best Regards,

    Michael.