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Discussion Groups | Comp.Arch.Embedded | tiny inductor with every bypass cap?
There are 68 messages in this thread.
You are currently looking at messages 60 to 68.
Re: tiny inductor with every bypass cap? - Terry Given - 18:08 23-06-08
Joerg wrote: > Terry Given wrote: > >> Joerg wrote: >> >>> John Larkin wrote: >>> >>>> On Sun, 22 Jun 2008 13:03:09 +0000, Guy Macon >>>> <http://www.guymacon.com/>; wrote: >>>> >>>>> >>>>> >>>>> John Larkin wrote: >>>>> >>>>>> Inductors don't generally help digital chips, and may actually reduce >>>>>> timing margins. We do use ferrite bead+capacitor filters on the >>>>>> supply >>>>>> rails of some fast opamps and adc's, to keep switcher noise and >>>>>> other-channel crosstalk from sneaking in. >>>>>> >>>>>> The best way to power big digital chips is with solid power planes, >>>>>> reasonably bypassed. That will present lower rail impedances than you >>>>>> could get by isolating the bypass caps on a per-pin basis. >>>>> >>>>> >>>>> Unless my design is cost sensitive, I generally put ferrite beads >>>>> on the wires coming from the power supply. I have never had this >>>>> actually change how well anything works, but I can see a bit less >>>>> noise with a scope, and doing it that way is fairly cheap. I have >>>>> seen all sorts of schemes for power/ground, but I have never seen >>>>> any thing that beats a solid ground plane and good physical placement >>>>> of sensitive / noise-producing sections. >>>> >>>> >>>> >>>> Any time you add inductance to a supply rail, the consequences should >>>> be analyzed. It could... >>>> >>>> Series resonate at some switching supply frequency and *increase* >>>> downstream ripple >>>> >>>> Add DC drop. With chip core voltages below 1 volt, and timing margins >>>> critical, that could get interesting >>>> >>>> If a chip can grossly shift its average current needs (like a uP, or >>>> some analog driver) the added L can make the supply dip. >>>> >>> >>> Or spike. Old rule with inductors: They want to maintain their >>> current no matter what. If they can't then they do what taxing >>> authorities do when they run out of dough: Raise the voltage ... >>> >>> >>>> The inductor could fry! >>>> >>>> >>>> I've seen all of these. >>>> >>> >>> Seen some grief in that domain as well. Including freaking expensive >>> FPGA that have become doorstops. >>> >> >> One design I looked at used a 600MHz agilent parallel/serial - >> serail/parallel chipset. there was a 1uH inductor between the 0V plane >> of the receiver/equaliser chip & the agilent serial/parallel chip 0V >> plane. >> >> oddly enough the serial link seemed a bit flaky. that didnt stop the >> company from selling hundreds of millions of dollars worth of product, >> but it did meant they could daisy chain 2 units, rather than the >> dozens they planned on. >> >> and there was no way I could convince their head of engineering this >> was a bad thing. OTOH they paid my bill, and I did fix a whole host of >> other problems. >> > > > Shhht! You are taking away a chunk of my source of income :-) > ditto. how'd you get on with your tricky transformer? Cheers Terry
Re: tiny inductor with every bypass cap? - Joerg - 18:17 23-06-08
Terry Given wrote: > Joerg wrote: >> Terry Given wrote: >> >>> Joerg wrote: >>> >>>> John Larkin wrote: >>>> >>>>> On Sun, 22 Jun 2008 13:03:09 +0000, Guy Macon >>>>> <http://www.guymacon.com/>; wrote: >>>>> >>>>>> >>>>>> >>>>>> John Larkin wrote: >>>>>> >>>>>>> Inductors don't generally help digital chips, and may actually >>>>>>> reduce >>>>>>> timing margins. We do use ferrite bead+capacitor filters on the >>>>>>> supply >>>>>>> rails of some fast opamps and adc's, to keep switcher noise and >>>>>>> other-channel crosstalk from sneaking in. >>>>>>> >>>>>>> The best way to power big digital chips is with solid power planes, >>>>>>> reasonably bypassed. That will present lower rail impedances than >>>>>>> you >>>>>>> could get by isolating the bypass caps on a per-pin basis. >>>>>> >>>>>> >>>>>> Unless my design is cost sensitive, I generally put ferrite beads >>>>>> on the wires coming from the power supply. I have never had this >>>>>> actually change how well anything works, but I can see a bit less >>>>>> noise with a scope, and doing it that way is fairly cheap. I have >>>>>> seen all sorts of schemes for power/ground, but I have never seen >>>>>> any thing that beats a solid ground plane and good physical placement >>>>>> of sensitive / noise-producing sections. >>>>> >>>>> >>>>> >>>>> Any time you add inductance to a supply rail, the consequences should >>>>> be analyzed. It could... >>>>> >>>>> Series resonate at some switching supply frequency and *increase* >>>>> downstream ripple >>>>> >>>>> Add DC drop. With chip core voltages below 1 volt, and timing margins >>>>> critical, that could get interesting >>>>> >>>>> If a chip can grossly shift its average current needs (like a uP, or >>>>> some analog driver) the added L can make the supply dip. >>>>> >>>> >>>> Or spike. Old rule with inductors: They want to maintain their >>>> current no matter what. If they can't then they do what taxing >>>> authorities do when they run out of dough: Raise the voltage ... >>>> >>>> >>>>> The inductor could fry! >>>>> >>>>> >>>>> I've seen all of these. >>>>> >>>> >>>> Seen some grief in that domain as well. Including freaking expensive >>>> FPGA that have become doorstops. >>>> >>> >>> One design I looked at used a 600MHz agilent parallel/serial - >>> serail/parallel chipset. there was a 1uH inductor between the 0V >>> plane of the receiver/equaliser chip & the agilent serial/parallel >>> chip 0V plane. >>> >>> oddly enough the serial link seemed a bit flaky. that didnt stop the >>> company from selling hundreds of millions of dollars worth of >>> product, but it did meant they could daisy chain 2 units, rather than >>> the dozens they planned on. >>> >>> and there was no way I could convince their head of engineering this >>> was a bad thing. OTOH they paid my bill, and I did fix a whole host >>> of other problems. >>> >> >> >> Shhht! You are taking away a chunk of my source of income :-) >> > > ditto. how'd you get on with your tricky transformer? > That project hasn't come off the ground yet. IOW the client has not given the go-ahead to start. Hopefully they will, it'll be interesting and they'd get a system where they wouldn't have a single competitor. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
Re: tiny inductor with every bypass cap? - Terry Given - 19:04 23-06-08
Joerg wrote: > Terry Given wrote: > >> Joerg wrote: >> >>> Terry Given wrote: >>> >>>> Joerg wrote: >>>> >>>>> John Larkin wrote: >>>>> >>>>>> On Sun, 22 Jun 2008 13:03:09 +0000, Guy Macon >>>>>> <http://www.guymacon.com/>; wrote: >>>>>> >>>>>>> >>>>>>> >>>>>>> John Larkin wrote: >>>>>>> >>>>>>>> Inductors don't generally help digital chips, and may actually >>>>>>>> reduce >>>>>>>> timing margins. We do use ferrite bead+capacitor filters on the >>>>>>>> supply >>>>>>>> rails of some fast opamps and adc's, to keep switcher noise and >>>>>>>> other-channel crosstalk from sneaking in. >>>>>>>> >>>>>>>> The best way to power big digital chips is with solid power planes, >>>>>>>> reasonably bypassed. That will present lower rail impedances >>>>>>>> than you >>>>>>>> could get by isolating the bypass caps on a per-pin basis. >>>>>>> >>>>>>> >>>>>>> >>>>>>> Unless my design is cost sensitive, I generally put ferrite beads >>>>>>> on the wires coming from the power supply. I have never had this >>>>>>> actually change how well anything works, but I can see a bit less >>>>>>> noise with a scope, and doing it that way is fairly cheap. I have >>>>>>> seen all sorts of schemes for power/ground, but I have never seen >>>>>>> any thing that beats a solid ground plane and good physical >>>>>>> placement >>>>>>> of sensitive / noise-producing sections. >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> Any time you add inductance to a supply rail, the consequences should >>>>>> be analyzed. It could... >>>>>> >>>>>> Series resonate at some switching supply frequency and *increase* >>>>>> downstream ripple >>>>>> >>>>>> Add DC drop. With chip core voltages below 1 volt, and timing margins >>>>>> critical, that could get interesting >>>>>> >>>>>> If a chip can grossly shift its average current needs (like a uP, or >>>>>> some analog driver) the added L can make the supply dip. >>>>>> >>>>> >>>>> Or spike. Old rule with inductors: They want to maintain their >>>>> current no matter what. If they can't then they do what taxing >>>>> authorities do when they run out of dough: Raise the voltage ... >>>>> >>>>> >>>>>> The inductor could fry! >>>>>> >>>>>> >>>>>> I've seen all of these. >>>>>> >>>>> >>>>> Seen some grief in that domain as well. Including freaking >>>>> expensive FPGA that have become doorstops. >>>>> >>>> >>>> One design I looked at used a 600MHz agilent parallel/serial - >>>> serail/parallel chipset. there was a 1uH inductor between the 0V >>>> plane of the receiver/equaliser chip & the agilent serial/parallel >>>> chip 0V plane. >>>> >>>> oddly enough the serial link seemed a bit flaky. that didnt stop the >>>> company from selling hundreds of millions of dollars worth of >>>> product, but it did meant they could daisy chain 2 units, rather >>>> than the dozens they planned on. >>>> >>>> and there was no way I could convince their head of engineering this >>>> was a bad thing. OTOH they paid my bill, and I did fix a whole host >>>> of other problems. >>>> >>> >>> >>> Shhht! You are taking away a chunk of my source of income :-) >>> >> >> ditto. how'd you get on with your tricky transformer? >> > > That project hasn't come off the ground yet. IOW the client has not > given the go-ahead to start. Hopefully they will, it'll be interesting > and they'd get a system where they wouldn't have a single competitor. > now that would be nice. I'm doing more and more work now with energy-efficient LED lighting. my current project is cramming a 10W PFC + triple current controller into the neck of a lightbulb. And its all plastic, so I cant get rid of any heat. Cheers Terry
Re: tiny inductor with every bypass cap? - Joerg - 19:27 23-06-08
Terry Given wrote: > Joerg wrote: >> Terry Given wrote: >> >>> Joerg wrote: >>> >>>> Terry Given wrote: >>>> >>>>> Joerg wrote: >>>>> >>>>>> John Larkin wrote: >>>>>> >>>>>>> On Sun, 22 Jun 2008 13:03:09 +0000, Guy Macon >>>>>>> <http://www.guymacon.com/>; wrote: >>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> John Larkin wrote: >>>>>>>> >>>>>>>>> Inductors don't generally help digital chips, and may actually >>>>>>>>> reduce >>>>>>>>> timing margins. We do use ferrite bead+capacitor filters on the >>>>>>>>> supply >>>>>>>>> rails of some fast opamps and adc's, to keep switcher noise and >>>>>>>>> other-channel crosstalk from sneaking in. >>>>>>>>> >>>>>>>>> The best way to power big digital chips is with solid power >>>>>>>>> planes, >>>>>>>>> reasonably bypassed. That will present lower rail impedances >>>>>>>>> than you >>>>>>>>> could get by isolating the bypass caps on a per-pin basis. >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> Unless my design is cost sensitive, I generally put ferrite beads >>>>>>>> on the wires coming from the power supply. I have never had >>>>>>>> this actually change how well anything works, but I can see a >>>>>>>> bit less noise with a scope, and doing it that way is fairly >>>>>>>> cheap. I have >>>>>>>> seen all sorts of schemes for power/ground, but I have never >>>>>>>> seen any thing that beats a solid ground plane and good physical >>>>>>>> placement >>>>>>>> of sensitive / noise-producing sections. >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> Any time you add inductance to a supply rail, the consequences >>>>>>> should >>>>>>> be analyzed. It could... >>>>>>> >>>>>>> Series resonate at some switching supply frequency and *increase* >>>>>>> downstream ripple >>>>>>> >>>>>>> Add DC drop. With chip core voltages below 1 volt, and timing >>>>>>> margins >>>>>>> critical, that could get interesting >>>>>>> >>>>>>> If a chip can grossly shift its average current needs (like a uP, or >>>>>>> some analog driver) the added L can make the supply dip. >>>>>>> >>>>>> >>>>>> Or spike. Old rule with inductors: They want to maintain their >>>>>> current no matter what. If they can't then they do what taxing >>>>>> authorities do when they run out of dough: Raise the voltage ... >>>>>> >>>>>> >>>>>>> The inductor could fry! >>>>>>> >>>>>>> >>>>>>> I've seen all of these. >>>>>>> >>>>>> >>>>>> Seen some grief in that domain as well. Including freaking >>>>>> expensive FPGA that have become doorstops. >>>>>> >>>>> >>>>> One design I looked at used a 600MHz agilent parallel/serial - >>>>> serail/parallel chipset. there was a 1uH inductor between the 0V >>>>> plane of the receiver/equaliser chip & the agilent serial/parallel >>>>> chip 0V plane. >>>>> >>>>> oddly enough the serial link seemed a bit flaky. that didnt stop >>>>> the company from selling hundreds of millions of dollars worth of >>>>> product, but it did meant they could daisy chain 2 units, rather >>>>> than the dozens they planned on. >>>>> >>>>> and there was no way I could convince their head of engineering >>>>> this was a bad thing. OTOH they paid my bill, and I did fix a whole >>>>> host of other problems. >>>>> >>>> >>>> >>>> Shhht! You are taking away a chunk of my source of income :-) >>>> >>> >>> ditto. how'd you get on with your tricky transformer? >>> >> >> That project hasn't come off the ground yet. IOW the client has not >> given the go-ahead to start. Hopefully they will, it'll be interesting >> and they'd get a system where they wouldn't have a single competitor. >> > > now that would be nice. > > I'm doing more and more work now with energy-efficient LED lighting. my > current project is cramming a 10W PFC + triple current controller into > the neck of a lightbulb. And its all plastic, so I cant get rid of any > heat. > That challenge will get even bigger. Many lamps in the US have these tiny "candlestick bulb" sockets. No energy saver bulbs exist, nada. That would be a market I think. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
Re: tiny inductor with every bypass cap? - Joel Koltner - 20:20 23-06-08
"Joerg" <n...@removethispacbell.net> wrote in message news:akW7k.10447$j...@flpi148.ffdc.sbc.com... > That challenge will get even bigger. Many lamps in the US have these tiny > "candlestick bulb" sockets. No energy saver bulbs exist, nada. You don't mean something like this: http://www.bulbs.com/eSpec.aspx?ID=12296&Ref=Compact+Fluorescent+Screw-in&RefId=20&Ref2=Light+Bulbs ...do you?
Re: tiny inductor with every bypass cap? - Terry Given - 20:25 23-06-08
Joerg wrote: > Terry Given wrote: > >> Joerg wrote: >> >>> Terry Given wrote: >>> >>>> Joerg wrote: >>>> >>>>> Terry Given wrote: >>>>> >>>>>> Joerg wrote: >>>>>> >>>>>>> John Larkin wrote: >>>>>>> >>>>>>>> On Sun, 22 Jun 2008 13:03:09 +0000, Guy Macon >>>>>>>> <http://www.guymacon.com/>; wrote: >>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> John Larkin wrote: >>>>>>>>> >>>>>>>>>> Inductors don't generally help digital chips, and may actually >>>>>>>>>> reduce >>>>>>>>>> timing margins. We do use ferrite bead+capacitor filters on >>>>>>>>>> the supply >>>>>>>>>> rails of some fast opamps and adc's, to keep switcher noise and >>>>>>>>>> other-channel crosstalk from sneaking in. >>>>>>>>>> >>>>>>>>>> The best way to power big digital chips is with solid power >>>>>>>>>> planes, >>>>>>>>>> reasonably bypassed. That will present lower rail impedances >>>>>>>>>> than you >>>>>>>>>> could get by isolating the bypass caps on a per-pin basis. >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> Unless my design is cost sensitive, I generally put ferrite beads >>>>>>>>> on the wires coming from the power supply. I have never had >>>>>>>>> this actually change how well anything works, but I can see a >>>>>>>>> bit less noise with a scope, and doing it that way is fairly >>>>>>>>> cheap. I have >>>>>>>>> seen all sorts of schemes for power/ground, but I have never >>>>>>>>> seen any thing that beats a solid ground plane and good >>>>>>>>> physical placement >>>>>>>>> of sensitive / noise-producing sections. >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> Any time you add inductance to a supply rail, the consequences >>>>>>>> should >>>>>>>> be analyzed. It could... >>>>>>>> >>>>>>>> Series resonate at some switching supply frequency and *increase* >>>>>>>> downstream ripple >>>>>>>> >>>>>>>> Add DC drop. With chip core voltages below 1 volt, and timing >>>>>>>> margins >>>>>>>> critical, that could get interesting >>>>>>>> >>>>>>>> If a chip can grossly shift its average current needs (like a >>>>>>>> uP, or >>>>>>>> some analog driver) the added L can make the supply dip. >>>>>>>> >>>>>>> >>>>>>> Or spike. Old rule with inductors: They want to maintain their >>>>>>> current no matter what. If they can't then they do what taxing >>>>>>> authorities do when they run out of dough: Raise the voltage ... >>>>>>> >>>>>>> >>>>>>>> The inductor could fry! >>>>>>>> >>>>>>>> >>>>>>>> I've seen all of these. >>>>>>>> >>>>>>> >>>>>>> Seen some grief in that domain as well. Including freaking >>>>>>> expensive FPGA that have become doorstops. >>>>>>> >>>>>> >>>>>> One design I looked at used a 600MHz agilent parallel/serial - >>>>>> serail/parallel chipset. there was a 1uH inductor between the 0V >>>>>> plane of the receiver/equaliser chip & the agilent serial/parallel >>>>>> chip 0V plane. >>>>>> >>>>>> oddly enough the serial link seemed a bit flaky. that didnt stop >>>>>> the company from selling hundreds of millions of dollars worth of >>>>>> product, but it did meant they could daisy chain 2 units, rather >>>>>> than the dozens they planned on. >>>>>> >>>>>> and there was no way I could convince their head of engineering >>>>>> this was a bad thing. OTOH they paid my bill, and I did fix a >>>>>> whole host of other problems. >>>>>> >>>>> >>>>> >>>>> Shhht! You are taking away a chunk of my source of income :-) >>>>> >>>> >>>> ditto. how'd you get on with your tricky transformer? >>>> >>> >>> That project hasn't come off the ground yet. IOW the client has not >>> given the go-ahead to start. Hopefully they will, it'll be >>> interesting and they'd get a system where they wouldn't have a single >>> competitor. >>> >> >> now that would be nice. >> >> I'm doing more and more work now with energy-efficient LED lighting. >> my current project is cramming a 10W PFC + triple current controller >> into the neck of a lightbulb. And its all plastic, so I cant get rid >> of any heat. >> > > That challenge will get even bigger. Many lamps in the US have these > tiny "candlestick bulb" sockets. No energy saver bulbs exist, nada. That > would be a market I think. > oh yes. its a real PITA making it PFC & dimmable too. about once a month I suggest getting Jim to design us some nice custom analog (I translated that for you ;) silicon; given we have found 4 different problems with "custom" chips from a certain vendor in CA who shall remain nameless (but whos initials are XX (not the letter X though)) - incuding a SMPS controller that, when it gets hot, loses feedback and increases Vout until things explode - I suspect I'll get my way eventually. Cheers Terry
Re: tiny inductor with every bypass cap? - Joerg - 20:36 23-06-08
Joel Koltner wrote: > "Joerg" <n...@removethispacbell.net> wrote in message > news:akW7k.10447$j...@flpi148.ffdc.sbc.com... >> That challenge will get even bigger. Many lamps in the US have these tiny >> "candlestick bulb" sockets. No energy saver bulbs exist, nada. > > You don't mean something like this: > http://www.bulbs.com/eSpec.aspx?ID=12296&Ref=Compact+Fluorescent+Screw-in&RefId=20&Ref2=Light+Bulbs > ...do you? > Yes, that socket. But a bulb that flares out so close to the socket would not possibly fit most of our lamps. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
Re: tiny inductor with every bypass cap? - rickman - 07:50 26-06-08
On Jun 23, 7:04 pm, Terry Given <my_n...@ieee.org> wrote: > Joerg wrote: > > > That project hasn't come off the ground yet. IOW the client has not > > given the go-ahead to start. Hopefully they will, it'll be interesting > > and they'd get a system where they wouldn't have a single competitor. > > now that would be nice. > > I'm doing more and more work now with energy-efficient LED lighting. my > current project is cramming a 10W PFC + triple current controller into > the neck of a lightbulb. And its all plastic, so I cant get rid of any heat. Can you try to hold down the RFI? I have seen several CFLs make enough trash to trigger my scope. A friend used one several years ago before they came down in price and got common. It messed up his IR remote control! Had to turn off the lamp to get it to work. Rick