SPDIF to TTL
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From: Winfield Hill on 8 Jun 2010 08:52 M.Randelzhofer wrote... > > "Dirk Bruere at NeoPax" asked... >> There are a number of circuits on the Net to do this. For example: >> http://sound.westhost.com/project85.htm >> In Fig 5 should that IC be a 74HC04 as stated, or 74HCU04? > > In the following schematics page 17 upper left corner, you see a working > solution (I have the eval board, its working nicely in coax SPDIF mode). > http://focus.ti.com/lit/an/slea035a/slea035a.pdf > > MIKE It's interesting that TI picks an 'U04. An 74LVC2GU04 to be exact. They do use this simple ac-coupled-circuit in a PurePath Digital reference design for their rather sophisticated custom silicon for high-performance audio. -- Thanks, - Win
From: Jim Thompson on 8 Jun 2010 11:27 On 8 Jun 2010 05:52:41 -0700, Winfield Hill <Winfield_member(a)newsguy.com> wrote: >M.Randelzhofer wrote... >> >> "Dirk Bruere at NeoPax" asked... >>> There are a number of circuits on the Net to do this. For example: >>> http://sound.westhost.com/project85.htm >>> In Fig 5 should that IC be a 74HC04 as stated, or 74HCU04? >> >> In the following schematics page 17 upper left corner, you see a working >> solution (I have the eval board, its working nicely in coax SPDIF mode). >> http://focus.ti.com/lit/an/slea035a/slea035a.pdf >> >> MIKE > > It's interesting that TI picks an 'U04. An 74LVC2GU04 > to be exact. They do use this simple ac-coupled-circuit > in a PurePath Digital reference design for their rather > sophisticated custom silicon for high-performance audio. 'U04' Variants have been used like this "forever". Some loonies have even been known to use them as amplifiers :-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | The only thing bipartisan in this country is hypocrisy
From: Winfield Hill on 8 Jun 2010 13:18 Jim Thompson wrote... > > On 8 Jun 2010 Winfield Hill wrote: > >> M.Randelzhofer wrote... >>> >>> "Dirk Bruere at NeoPax" asked... >>>> There are a number of circuits on the Net to do this. >>>> For example: http://sound.westhost.com/project85.htm >>>> In Fig 5 should that IC be a 74HC04 as stated, or 74HCU04? >>> >>> In the following schematics page 17 upper left corner, you see >>> a working solution (I have the eval board, its working nicely >>> in coax SPDIF mode). >>> http://focus.ti.com/lit/an/slea035a/slea035a.pdf >>> >>> MIKE >> >> It's interesting that TI picks an 'U04. An 74LVC2GU04 >> to be exact. They do use this simple ac-coupled-circuit >> in a PurePath Digital reference design for their rather >> sophisticated custom silicon for high-performance audio. > > 'U04' Variants have been used like this "forever". Some > loonies have even been known to use them as amplifiers :-) Right, I'm well aware of that. Old stuff, dating back to the 60s when I started using cmos, or COS/MOS as RCA called it back then. But the question was about the viability of non-U types for this, do you have an opinion about that? Not what's naturally best, but whether it'll work OK. -- Thanks, - Win
From: Jim Thompson on 8 Jun 2010 16:44 On 8 Jun 2010 10:18:55 -0700, Winfield Hill <Winfield_member(a)newsguy.com> wrote: >Jim Thompson wrote... >> >> On 8 Jun 2010 Winfield Hill wrote: >> >>> M.Randelzhofer wrote... >>>> >>>> "Dirk Bruere at NeoPax" asked... >>>>> There are a number of circuits on the Net to do this. >>>>> For example: http://sound.westhost.com/project85.htm >>>>> In Fig 5 should that IC be a 74HC04 as stated, or 74HCU04? >>>> >>>> In the following schematics page 17 upper left corner, you see >>>> a working solution (I have the eval board, its working nicely >>>> in coax SPDIF mode). >>>> http://focus.ti.com/lit/an/slea035a/slea035a.pdf >>>> >>>> MIKE >>> >>> It's interesting that TI picks an 'U04. An 74LVC2GU04 >>> to be exact. They do use this simple ac-coupled-circuit >>> in a PurePath Digital reference design for their rather >>> sophisticated custom silicon for high-performance audio. >> >> 'U04' Variants have been used like this "forever". Some >> loonies have even been known to use them as amplifiers :-) > > Right, I'm well aware of that. Old stuff, dating back to > the 60s when I started using cmos, or COS/MOS as RCA called > it back then. But the question was about the viability of > non-U types for this, do you have an opinion about that? > Not what's naturally best, but whether it'll work OK. It'll function. The problem I have with it is: an 'HC04 is effectively THREE 'HCU04's in series, with size scaling for the gate-source capacitance build-up. So a low-pass feed-back biases at considerable rail-to-rail current. It'll function, but I don't recommend it. For my custom stuff, where such an animal is absolutely needed, I add current sources in the respective (device) sources to limit bias build-up. In a recent "monster" actuator driver I resorted to inverters where one side was a mirror until "swifty" speeds could be assured. ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | The only thing bipartisan in this country is hypocrisy
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