const-current thing
in [Design]
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From: krw on 25 May 2010 19:09 On Tue, 25 May 2010 10:38:39 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote: >On Tue, 25 May 2010 10:28:42 -0700, John Larkin ><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > >> >>Most cool: >> >>http://www.onsemi.com/pub/Collateral/NSI45020-D.PDF >> >>I've been wanting constant-current ICs for years. They are finally >>starting to happen. >> >>This is 51 cents, q1. >> >>John > >Fig 2 is pretty gross. Lousy headroom design. Sheeesh! What's that negative resistance all about?
From: Phil Hobbs on 25 May 2010 19:11 On 5/25/2010 6:56 PM, John Larkin wrote: > On Tue, 25 May 2010 18:33:55 -0400, Phil Hobbs > <pcdhSpamMeSenseless(a)electrooptical.net> wrote: > >> On 5/25/2010 1:38 PM, Jim Thompson wrote: >>> On Tue, 25 May 2010 10:28:42 -0700, John Larkin >>> <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>> >>>> >>>> Most cool: >>>> >>>> http://www.onsemi.com/pub/Collateral/NSI45020-D.PDF >>>> >>>> I've been wanting constant-current ICs for years. They are finally >>>> starting to happen. >>>> >>>> This is 51 cents, q1. >>>> >>>> John >>> >>> Fig 2 is pretty gross. Lousy headroom design. Sheeesh! >>> >>> ...Jim Thompson >> >> Figure 5 is what has me worried. A 15% current decrease occurs over >> seconds. >> >> Great idea, no cigar for the implementation. Still, it's a lot cheaper >> than the LTC thing. >> >> Cheers >> >> Phil Hobbs > > It would be good for gross stuff, like pushing current into a zener to > power some opamps floating on a power rail. It could also be a > protective current limiter. > > Laser-trimmed precise 2-terminal current limiters would be great, in > the 1 mA ballpark. Or 3-terminal, programmable with one resistor. > > John > Agreed. OTOH you can do a lot with an LM317L and a resistor. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
From: Phil Hobbs on 25 May 2010 19:13 On 5/25/2010 6:53 PM, Jamie wrote: > John Larkin wrote: > >> Most cool: >> >> http://www.onsemi.com/pub/Collateral/NSI45020-D.PDF >> >> I've been wanting constant-current ICs for years. They are finally >> starting to happen. >> >> This is 51 cents, q1. >> >> John >> > http://www.centralsemi.com/product/cld/index.aspx > > > Those are fairly horrible below 10 volts. You're way better off with an LM317L or LM334. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
From: krw on 25 May 2010 20:00 On Tue, 25 May 2010 15:56:28 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >On Tue, 25 May 2010 18:33:55 -0400, Phil Hobbs ><pcdhSpamMeSenseless(a)electrooptical.net> wrote: > >>On 5/25/2010 1:38 PM, Jim Thompson wrote: >>> On Tue, 25 May 2010 10:28:42 -0700, John Larkin >>> <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>> >>>> >>>> Most cool: >>>> >>>> http://www.onsemi.com/pub/Collateral/NSI45020-D.PDF >>>> >>>> I've been wanting constant-current ICs for years. They are finally >>>> starting to happen. >>>> >>>> This is 51 cents, q1. >>>> >>>> John >>> >>> Fig 2 is pretty gross. Lousy headroom design. Sheeesh! >>> >>> ...Jim Thompson >> >>Figure 5 is what has me worried. A 15% current decrease occurs over >>seconds. >> >>Great idea, no cigar for the implementation. Still, it's a lot cheaper >>than the LTC thing. >> >>Cheers >> >>Phil Hobbs > >It would be good for gross stuff, like pushing current into a zener to >power some opamps floating on a power rail. It could also be a >protective current limiter. Noise? >Laser-trimmed precise 2-terminal current limiters would be great, in >the 1 mA ballpark. Or 3-terminal, programmable with one resistor. > >John
From: Joerg on 25 May 2010 20:49
Jan Panteltje wrote: > On a sunny day (Tue, 25 May 2010 10:28:42 -0700) it happened John Larkin > <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in > <p22ov5d4ju2fn3pf69ttkvqru1s5aumsqe(a)4ax.com>: > >> Most cool: >> >> http://www.onsemi.com/pub/Collateral/NSI45020-D.PDF >> >> I've been wanting constant-current ICs for years. They are finally >> starting to happen. >> >> This is 51 cents, q1. >> >> John > > These dat 20 mA is a bit high for LEDs used as indicator. > I have some green ones now at 3.3V with 33k (!) in series, > the LEDs drop 2.38 and 2.44 V, so that makes .92 and .86 V over > the resistors, giving a current of about 28 uA, good visibiliy > in bright room light, JUST not blinding when you look directly into it. > ftp://panteltje.com/pub/low_current_LEDs_img_1964.jpg > The blue one is on 10% PWM with 180 Ohm in series on 3.3 V. > That current source product may not sell. > Resistors are cheaper. > Digikey would not have over 37,000 (as in thousand) of these in stock if they didn't sell. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. |