On Tue, 7 Sep 2021 22:46:51 -0700, John Robertson <spam@flippers.com> wrote:>On 2021/09/07 5:53 p.m., John Larkin wrote: >> On Tue, 7 Sep 2021 17:44:48 -0700, John Robertson <spam@flippers.com> >> wrote: >> >>> On 2021/09/07 2:03 p.m., John Larkin wrote: >>>> On Tue, 7 Sep 2021 13:55:14 -0700, John Robertson <spam@flippers.com> >>>> wrote: >>>> >>>>> On 2021/09/04 8:47 p.m., bitrex wrote: >>>>>> On 9/4/2021 11:41 PM, bitrex wrote: >>>>>>> On 9/4/2021 10:26 PM, Rick C wrote: >>>>>>>> On Saturday, September 4, 2021 at 9:13:13 PM UTC-4, bitrex wrote: >>>>>>>>> On 9/4/2021 7:33 PM, John Robertson wrote: >>>>>>>>>> Working on a FPGA project and we need perhaps 30 level shifter gates. >>>>>>>>>> >>>>>>>>>> Anyone work with 3.6 to 5.0 volt interfaces that can recommend any >>>>>>>>>> single part over the rest before I spend a few hours digging through >>>>>>>>>> Digi/Mouser/Newark's inventory? >>>>>>>>>> >>>>>>>>>> In some cases we can get away with resistors, but there is a bit of >>>>>>>>>> TTL >>>>>>>>>> level drivers needed. >>>>>>>>>> >>>>>>>>>> Thanks! >>>>>>>>>> >>>>>>>>>> John :-#)# >>>>>>>>> Sounding like a broken record proselytizing these things but a >>>>>>>>> number of >>>>>>>>> the Greenpak SPLCs have dual rails so you can have level-shifted IO of >>>>>>>>> arbitrary configuration, they're pretty cheap in quantity, and the mfgr >>>>>>>>> will program them for you. >>>>>>>>> >>>>>>>>> <https://www.dialog-semiconductor.com/products/greenpak> >>>>>>>>> >>>>>>>>> And you can put some logic in 'em, too! >>>>>>>> >>>>>>>> I'm glad you do keep mentioning them.� I believe they are pretty >>>>>>>> cheap in quantity, no?� You develop your program and they supply them >>>>>>>> for production already programmed, no?� Can they compete with a 10 >>>>>>>> bit shifter that costs a quarter?� What's the propagation delay pin >>>>>>>> to pin as buffers? >>>>>>>> >>>>>>> >>>>>>> >>>>>>> I think the cheapest device with the capability to 10 bit de-serialize >>>>>>> (if that's what you mean would be the SLG47503, 30 cents programmed in >>>>>>> quantities of 500, 25 cents in quantities of 3000+. I think you would >>>>>>> need at least 14 GPIO for 10 outputs plus input, clock, and reset, as >>>>>>> they tend to come in even numbers of GPIO. >>>>>>> >>>>>>> If you can get away with 12 GPIO somehow the SLG46855 is 25 cent >>>>>>> programmed for 500, 20 for 3000+: >>>>>> >>>>>> And if you need 10,000+ looks like they'd likely be amenable to go even >>>>>> lower than that. >>>>>> >>>>> >>>>> We only need a few hundred or so shifters, so your suggestion won't help >>>>> this time - will keep it in mind though! We are likely going with the >>>>> 74AC245 or similar for my application, just need two or so of them per >>>>> PCB and perhaps 50 to 100 PCBs... >>>>> >>>>> We are also likely using the MAX10 FPGA. >>>>> >>>>> Thanks for your suggestions! >>>>> >>>>> John :-#)# >>>> >>>> Are you translating 3.3 up to 5? An AC245 might fry doing that. >>>> >>>> Use HCT. >>>> >>> >>> 74ACT245 allows for TTL inputs...however spotted the TI SN74AVCxTXX >>> series, but it looks more expensive. >>> >>> This is for interfacing a MAX10 FPGA to mid-70s TTL. >>> >>> John :-#)# >> >> Good ole bipolar TTL had a logic threshold near 1.2 volts. It would >> work fine from a 3.3 volt swing. >> > >Yes, that would probably be OK for one direction, but I don't think 3.3 >logic likes TTL drive voltages...these buffers are for the 6802 based >CPU TTL level bus as well. > >TI makes some bidirectional translators that are of interest - trying to >keep the costs down, so also seeing what Bitrex can come up with with >the GreenPAK devices - one needs some quantity, but $0.25 for an 8 bit >(more?) IO is hard to beat - but the learning curve to create the part >looks intense. > >John :-#)#Classic TTL output was about 3.5 volts, but a soft pulldown, 5 mA maybe, would reduce that to about +3. So 1K to ground would be about right. -- Father Brown's figure remained quite dark and still; but in that instant he had lost his head. His head was always most valuable when he had lost it.
Looking for SMD level shifters to TTL
Started by ●September 4, 2021
Reply by ●September 8, 20212021-09-08
Reply by ●September 8, 20212021-09-08
On Tuesday, September 7, 2021 at 5:02:37 PM UTC-4, John Robertson wrote:> On 2021/09/04 8:47 p.m., bitrex wrote: > > On 9/4/2021 11:41 PM, bitrex wrote: > >> On 9/4/2021 10:26 PM, Rick C wrote: > >>> On Saturday, September 4, 2021 at 9:13:13 PM UTC-4, bitrex wrote: > >>>> On 9/4/2021 7:33 PM, John Robertson wrote: > >>>>> Working on a FPGA project and we need perhaps 30 level shifter gates. > >>>>> > >>>>> Anyone work with 3.6 to 5.0 volt interfaces that can recommend any > >>>>> single part over the rest before I spend a few hours digging through > >>>>> Digi/Mouser/Newark's inventory? > >>>>> > >>>>> In some cases we can get away with resistors, but there is a bit of > >>>>> TTL > >>>>> level drivers needed. > >>>>> > >>>>> Thanks! > >>>>> > >>>>> John :-#)# > >>>> Sounding like a broken record proselytizing these things but a > >>>> number of > >>>> the Greenpak SPLCs have dual rails so you can have level-shifted IO of > >>>> arbitrary configuration, they're pretty cheap in quantity, and the mfgr > >>>> will program them for you. > >>>> > >>>> <https://www.dialog-semiconductor.com/products/greenpak> > >>>> > >>>> And you can put some logic in 'em, too! > >>> > >>> I'm glad you do keep mentioning them. I believe they are pretty > >>> cheap in quantity, no? You develop your program and they supply them > >>> for production already programmed, no? Can they compete with a 10 > >>> bit shifter that costs a quarter? What's the propagation delay pin > >>> to pin as buffers? > >>> > >> > >> > >> I think the cheapest device with the capability to 10 bit de-serialize > >> (if that's what you mean would be the SLG47503, 30 cents programmed in > >> quantities of 500, 25 cents in quantities of 3000+. I think you would > >> need at least 14 GPIO for 10 outputs plus input, clock, and reset, as > >> they tend to come in even numbers of GPIO. > >> > >> If you can get away with 12 GPIO somehow the SLG46855 is 25 cent > >> programmed for 500, 20 for 3000+: > > > > And if you need 10,000+ looks like they'd likely be amenable to go even > > lower than that. > > > Looks like you know this GreenPAK stuff - which of their devices would > easily compete with 74AC245 in 500 lot pricing? Can one add input > protection to the chip and how many non-inverting gates are possible? > > This would be for interfacing either with a 1mHz CPU Bus and also I/O > with the outside world - TTL levels expected, and interfacing to a MAX10 > FPGA... > > Do they have a good supply time?One big potential issue with a single sourced part like the GreenPak devices is the potential for non-delivery. I had a part become unobtanium when the factory burned down. Now a $3 part is $100. Yup. It happens. A part like the SN74CBTD3384CPW quickswitch device is multi-sourced and made in many factories and is quite cheap without custom programming. 10 bits of bi-directional level limiting for $0.25. Hard to beat. -- Rick C. -- Get 1,000 miles of free Supercharging -- Tesla referral code - https://ts.la/richard11209
Reply by ●September 8, 20212021-09-08
Rick C <gnuarm.deletethisbit@gmail.com> wrote:> > A part like the SN74CBTD3384CPW quickswitch device is multi-sourced > and made in many factories and is quite cheap without custom > programming. 10 bits of bi-directional level limiting for $0.25. > Hard to beat. >I would call this part "level clamping", It is good for 5 V -> 3.3 Volt. But 3.3 V -> 5 Volt can not be done with it. -- Uwe Bonnes bon@elektron.ikp.physik.tu-darmstadt.de Institut fuer Kernphysik Schlossgartenstrasse 9 64289 Darmstadt --------- Tel. 06151 1623569 ------- Fax. 06151 1623305 ---------
Reply by ●September 8, 20212021-09-08
On Wednesday, 8 September 2021 at 18:30:18 UTC+1, Uwe Bonnes wrote:> Rick C <gnuarm.del...@gmail.com> wrote: > > > > A part like the SN74CBTD3384CPW quickswitch device is multi-sourced > > and made in many factories and is quite cheap without custom > > programming. 10 bits of bi-directional level limiting for $0.25. > > Hard to beat. > > > I would call this part "level clamping", It is good for 5 V -> 3.3 > Volt. But 3.3 V -> 5 Volt can not be done with it.Yes, but TTL is happy receiving 3.3V CMOS levels, so there is no problem. Also, most TTL drivers only have weak pullups, so the CMOS inputs can usually just rely on their clamping diodes. John
Reply by ●September 8, 20212021-09-08
On Wednesday, September 8, 2021 at 10:30:18 AM UTC-7, Uwe Bonnes wrote:> Rick C <gnuarm.del...@gmail.com> wrote: > > > > A part like the SN74CBTD3384CPW quickswitch device ...> I would call this part "level clamping", It is good for 5 V -> 3.3 > Volt. But 3.3 V -> 5 Volt can not be done with it.But, 5V TTL does not need 5V logic levels, only 3V or so; it's only 5V CMOS that benefits from higher Vin(high). 3.3V CMOS levels are just dandy as TTL inputs, as long as the current sinking is sufficient. Mostly, that means 74S gates are not compatible...
Reply by ●September 8, 20212021-09-08
On Wednesday, September 8, 2021 at 1:30:18 PM UTC-4, Uwe Bonnes wrote:> Rick C <gnuarm.del...@gmail.com> wrote: > > > > A part like the SN74CBTD3384CPW quickswitch device is multi-sourced > > and made in many factories and is quite cheap without custom > > programming. 10 bits of bi-directional level limiting for $0.25. > > Hard to beat. > > > I would call this part "level clamping", It is good for 5 V -> 3.3 > Volt. But 3.3 V -> 5 Volt can not be done with it.If you are driving CMOS levels, that is true, but no one uses 5V CMOS. TTL was the standard indicated above which 3.3V CMOS drives quite well. These parts prevent the 5V input on the TTL part from pulling up the 3.3V signal. So unless there is a requirement to drive 5V CMOS which was not stated, these parts work well. I'm using them in a 13 year old design of which I am working on delivering another 10,000 units. The real beauty of these parts is they are inherently bidirectional (like a wire), so no need to worry with direction controls or even which direction the signals pass. They also work well interfacing 3.3V and 5V I2C signals. -- Rick C. -+ Get 1,000 miles of free Supercharging -+ Tesla referral code - https://ts.la/richard11209
