I have successfully used a 74LVC1G34DBV to do exactly that, 5V supply, 10u & 100n on the supply, 499R in series on the output, driven from 3v3 LVTTL.
Run at 5V the WS2812B has Vil/Vih of 0.9 and 3.5 V. Hence you need more than LVTTL or TTL logic levels. I would be surprised if a pull up was a good solution, at 800 kHz you wish transition times on the order of 75 ns : PU dissipation ? The essential spec for a WS2812 buffer / driver device is TTL input levels, 5V CMOS output levels : the usu suspects are 74LVC and 74HCT Martin -----Original Message----- From: Adrian Godwin [mailto:[email protected]] Sent: 30 July 2025 22:29 To: Martin Bishop <[email protected]> Cc: General Discussion: On-Topic and Off-Topic Posts <[email protected]>; Paul Koning <[email protected]> Subject: Re: [cctalk] Re: RP2350 5V Input Tollerant Pins I was thinking specifically of ws2812 addressable leds which have CMOS levels. The data stream is fairly slow (~800kHz) and can usually be generated from 3v3 with the common FET voltage shifter (which also has passive pullup). It's sometimes driven with 3v3 but is marginal. I was thinking that it might be driven bye a 2350 with a 5V pullup more reliably. On Wed, Jul 30, 2025 at 11:19 PM Martin Bishop <[email protected]> wrote: > > Adrian > > The summary answer to your questions must be "in general no" : 5V CMOS levels > are quite different from TTL levels and open drain /collector signalling is > inherently slow. > > 5V CMOS, with its very high Vih (typ > 3.5V), is one of those things it is > nice not to have to work with. If you do have to drive it then, in general, > logic (level) translation families are necessary. > > Contrariwise, 3v3 LVTTL and 5V TTL thresholds are essentially equal Vil at > 0v8 and Vih at 2V. However, 5V pull ups and transients make 5V --> 3v3 > connections an invitation to smoking : YMMV. > > If you have a specific interfacing problem, the essential information to > select a way ahead is source chip, sink chip, signal speed, and constraints. > > The can being kicked in this thread was the RP2050's 5V tollerant input, > which should make it useable for direct connection to TTL, then some apparent > "documentation" issues were identified ... > > Some "handy primers" are: > https://www.ti.com/lit/pdf/sdyu001?keyMatch=logic%20families&tisearch= > universal_search see page 4 for typ logic levels > https://www.ti.com/lit/pdf/ssztc76?keyMatch=logic%20families&tisearch= > universal_search > https://www.ti.com/lit/pdf/scyt129?keyMatch=little%20logic&tisearch=un > iversal_search > https://www.ti.com/lit/pdf/scyb018?keyMatch=voltage%20level%20translat > ion%20guide&tisearch=universal_search > > Martin > > -----Original Message----- > From: Adrian Godwin [mailto:[email protected]] > Sent: 30 July 2025 21:33 > To: General Discussion: On-Topic and Off-Topic Posts > <[email protected]> > Cc: Martin Bishop <[email protected]>; Paul Koning > <[email protected]> > Subject: Re: [cctalk] Re: RP2350 5V Input Tollerant Pins > > What about output pins in open-drain mode with a 5V pullup ? Can they provide > a 5V CMOS-compatible output ? > > On Wed, Jul 30, 2025 at 9:40 PM Paul Koning via cctalk > <[email protected]> wrote: > > > > > > > > > On Jul 30, 2025, at 3:07 PM, Martin Bishop > > > <[email protected]> wrote: > > > > > > https://www.eenewseurope.com/en/raspberry-pi-spins-its-rp2350-adds-5v-support/ > > > was my point of departure, doubtless a recycled press release. > > > > Yikes. Assuming that is accurate, Raspberry Pi screwed up very severely by > > claiming 5V support in the data sheet without saying it only applies to the > > A4 rev. Any number of people will fry their chips because of this blunder. > > > > paul
