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Re: LF: Softrock RX divider IC problem, unexpected frequency out

from [Andy Talbot] [Permanent Link][Original]
To: LineOne <[email protected]>
Subject: Re: LF: Softrock RX divider IC problem, unexpected frequency out
From: Andy Talbot <[email protected]>
Date: Wed, 31 Jan 2018 15:31:16 +0000
Cc: Chris Wilson <[email protected]>
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If you only have supply of 0/5V you cannot have a negative '0' level.   
If your scope shows it, then it is possible your scope ground is not connected properly yo the -ve rail but instead to somehting further back showing a small 0.5V drop
or  teh scope needs setting up

Don't worry about it.  The wqaveform looks perfect - very nearly 1:1 square wave - its what happens when you do a design properly
Now worry about sorting out the divider.

Andy


On 31 January 2018 at 15:09, Chris Wilson <[email protected]> wrote:


Hello Claudio,


Thanks  Claudio,  but  how  do  I  fix this issue? I can rebuild an F1
engine, but this is outside my comfort zone :)

Wednesday, January 31, 2018, 2:34:33 PM, you wrote:

>
> On Wednesday 31 January 2018 11:19:51 you wrote:
>
>> I don't know I was wondering that myself. Is it significant?
>
>
>
> If the HIGH level is too low the following divider can't divide properly!
>
>
>
> If the LOW level can sink few mA of current from the IC  the divider can be degraded!
>
>
>
> Random divide factor can be a consequence.
>
>
>
> from 74HC74 data sheet, see the VIH and VIL
>
>
>
>
>
>
> Regards
>
> Claudio
>
>



--
Best regards,
 Chris                            mailto:[email protected]



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