On 06/11/2021 09:45 AM, Jim Palladino wrote:
Hi Marcus,
Right -- the output of the Octoclock is 5V. I'm not seeing how the
N320 can accept that as an input. The knowledge base article says the
N320 expects 5Vpp at the 1pps input. But the schematics/parts data
sheet for the input buffer don't seem to support that . . . unless I'm
missing something.
Thanks,
Jim
It certainly looks like a potential problem, but I haven't heard of
anyone having 1PPS failure issues on the N320 when used with
Octoclock--pretty sure it was tested with Octoclock prior to
release. But I'll check with R&D.
------------------------------------------------------------------------
*From:* Marcus D. Leech <patchvonbr...@gmail.com>
*Sent:* Friday, June 11, 2021 9:39 AM
*To:* usrp-users@lists.ettus.com <usrp-users@lists.ettus.com>
*Subject:* [USRP-users] Re: N320 1PPS input voltage
On 06/11/2021 09:11 AM, Marcus Müller wrote:
> Hello Jim,
>
>
> hm, that knowledge base article must be wrong: The octoclock
internally only has a 3.3V
> supply. But before I say something wrong here, let me check back.
>
>
> Best regards,
>
> Marcus
The 1PPS outputs on the Octoclock are bufered by 7404 inverters, which
appear to have a 5V Vcc.
>
>
> On 11.06.21 14:17, Jim Palladino wrote:
>
>> Hello,
>>
>> We are planning on using an octoclock with several devices,
including an N320. The
>> octoclock outputs a 5V 1pps signal, but I'm confused about the N320
1pps input.
>>
>> According to
(https://urldefense.proofpoint.com/v2/url?u=https-3A__kb.ettus.com_N320_N321-29-3A&d=DwIF-g&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=XUEEtUEfpaAEGxRI-WGuqHauOvsPdD2NZkfwDnwpYx0&m=-9vS_HYCWF4BKKIX7QR3SO2LJ3yD1MyEElYsX5a8WMs&s=TdFHQJNItGehIsL1D4yXezIfq_vO05AvF1_lMSyNpHs&e=
>> "PPS - Pulse Per Second Using a PPS signal for timestamp
synchronization requires a
>> square wave signal with the following a 5Vpp amplitude."
>>
>> If I look at the schematics for the N320, on page 15,
>>
(https://urldefense.proofpoint.com/v2/url?u=https-3A__kb.ettus.com_images_f_f4_USRP-5FN3XX-5FMB-5FSchematic.pdf&d=DwIF-g&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=XUEEtUEfpaAEGxRI-WGuqHauOvsPdD2NZkfwDnwpYx0&m=-9vS_HYCWF4BKKIX7QR3SO2LJ3yD1MyEElYsX5a8WMs&s=6JTHdP9IoYFRQhn24LgJjEofkuFwgAsHTs9iHhgMuBg&e=)
they show that the input
>> 1pps signal goes through an NC7SV157. Vcc for that is 3.3V in the
schematics.
>>
>> According to the datasheet, the absolute maximum rating on the
input is 4.3V.
>>
"https://urldefense.proofpoint.com/v2/url?u=https-3A__www.onsemi.com_pdf_datasheet_nc7sv157-2Dd.pdf&d=DwIF-g&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=XUEEtUEfpaAEGxRI-WGuqHauOvsPdD2NZkfwDnwpYx0&m=-9vS_HYCWF4BKKIX7QR3SO2LJ3yD1MyEElYsX5a8WMs&s=XPmiCDRDfM2wVtI1g4KChC9dkOJhMyrqBTMv_Rx01Xg&e=";
>>
>> So, I'm not sure how the N320 can safely accept a 5V input (from
the octoclock or other
>> device).
>>
>> Thanks,
>> Jim
>>
>>
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