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From: Joerg on 25 Jul 2010 18:08 John Larkin wrote: > On Sun, 25 Jul 2010 14:39:46 -0700, Joerg <invalid(a)invalid.invalid> > wrote: > >> John Larkin wrote: >>> I spent most of the day building this. >>> >>> ftp://jjlarkin.lmi.net/V220_Test_Front.jpg >>> >>> ftp://jjlarkin.lmi.net/V220_Test_Back.jpg >>> >>> which is a fixture to help test/cal a new VME module. It's powered by >>> a 48-volt wall wart. Those old-fashioned teevee type terminal strips, >>> and rotary switches, are pretty cool. This really deserves a more >>> macho knob, but that's all I could find around the place without >>> stealing one from something in the antique collection. >>> >>> The thing it connects to has 13 ARM processors and one FPGA on the >>> board. Time warp. >>> >>> ftp://jjlarkin.lmi.net/V220_top.jpg >>> >> Do I see three tantalums on the bottom right? Oh-oh ... :-) > > Yes. LM1117's like tantalums on their outputs; the ESR is just right, > and will hold up at -20C. They are all 22u, 10v, 11 cents each, on the > outputs of 3.3, 2.5, and 1.25 volt regulators. That should be safe. > > Why make rules if you can't break them once in a while? > > The 1.25 is FPGA core voltage; that's an LM1117 with its adj pin > grounded. The 2.5 is FPGA VCCaux, another LM1117 with its adj pin tied > to the 1.25 rail. I would happily show the programming resistor > values, except there aren't any. > Well, if you have good experience with the LM1117 maybe it works. I just don't trust LDOs anymore, too much grief. Only one was my own design and only because the client absolutely insisted on a particular LDO to be used. Then, sure enough ... *PHOOF* ... *POP* -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Joerg on 25 Jul 2010 18:10 krw(a)att.bizzzzzzzzzzzz wrote: > On Sun, 25 Jul 2010 14:39:46 -0700, Joerg <invalid(a)invalid.invalid> wrote: > >> John Larkin wrote: >>> I spent most of the day building this. >>> >>> ftp://jjlarkin.lmi.net/V220_Test_Front.jpg >>> >>> ftp://jjlarkin.lmi.net/V220_Test_Back.jpg >>> >>> which is a fixture to help test/cal a new VME module. It's powered by >>> a 48-volt wall wart. Those old-fashioned teevee type terminal strips, >>> and rotary switches, are pretty cool. This really deserves a more >>> macho knob, but that's all I could find around the place without >>> stealing one from something in the antique collection. >>> >>> The thing it connects to has 13 ARM processors and one FPGA on the >>> board. Time warp. >>> >>> ftp://jjlarkin.lmi.net/V220_top.jpg >>> >> Do I see three tantalums on the bottom right? Oh-oh ... :-) > > Your replacement is? Ceramics. Cheap. If an LDO is used (I always recommend not to do that) and it requires a particular ESR range you can place resistors in series. At least then you can be sure what the ESR is. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: John Larkin on 25 Jul 2010 18:54 On Sun, 25 Jul 2010 15:08:52 -0700, Joerg <invalid(a)invalid.invalid> wrote: >John Larkin wrote: >> On Sun, 25 Jul 2010 14:39:46 -0700, Joerg <invalid(a)invalid.invalid> >> wrote: >> >>> John Larkin wrote: >>>> I spent most of the day building this. >>>> >>>> ftp://jjlarkin.lmi.net/V220_Test_Front.jpg >>>> >>>> ftp://jjlarkin.lmi.net/V220_Test_Back.jpg >>>> >>>> which is a fixture to help test/cal a new VME module. It's powered by >>>> a 48-volt wall wart. Those old-fashioned teevee type terminal strips, >>>> and rotary switches, are pretty cool. This really deserves a more >>>> macho knob, but that's all I could find around the place without >>>> stealing one from something in the antique collection. >>>> >>>> The thing it connects to has 13 ARM processors and one FPGA on the >>>> board. Time warp. >>>> >>>> ftp://jjlarkin.lmi.net/V220_top.jpg >>>> >>> Do I see three tantalums on the bottom right? Oh-oh ... :-) >> >> Yes. LM1117's like tantalums on their outputs; the ESR is just right, >> and will hold up at -20C. They are all 22u, 10v, 11 cents each, on the >> outputs of 3.3, 2.5, and 1.25 volt regulators. That should be safe. >> >> Why make rules if you can't break them once in a while? >> >> The 1.25 is FPGA core voltage; that's an LM1117 with its adj pin >> grounded. The 2.5 is FPGA VCCaux, another LM1117 with its adj pin tied >> to the 1.25 rail. I would happily show the programming resistor >> values, except there aren't any. >> > >Well, if you have good experience with the LM1117 maybe it works. I just >don't trust LDOs anymore, too much grief. Only one was my own design and >only because the client absolutely insisted on a particular LDO to be >used. Then, sure enough ... *PHOOF* ... *POP* The 1117 is basically an LM317 architecture with a little less dropout. The final pass transistor is an NPN, so the open-loop output impedance is relatively low. They are rugged, cheap, and stable if you put a tantalum or aluminum on their output. I use them as power amps, too, driving the adj pin with an opamp. John
From: Jim Thompson on 25 Jul 2010 18:54 On Sun, 25 Jul 2010 15:54:57 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >On Sun, 25 Jul 2010 15:08:52 -0700, Joerg <invalid(a)invalid.invalid> >wrote: > >>John Larkin wrote: >>> On Sun, 25 Jul 2010 14:39:46 -0700, Joerg <invalid(a)invalid.invalid> >>> wrote: >>> >>>> John Larkin wrote: >>>>> I spent most of the day building this. >>>>> >>>>> ftp://jjlarkin.lmi.net/V220_Test_Front.jpg >>>>> >>>>> ftp://jjlarkin.lmi.net/V220_Test_Back.jpg >>>>> >>>>> which is a fixture to help test/cal a new VME module. It's powered by >>>>> a 48-volt wall wart. Those old-fashioned teevee type terminal strips, >>>>> and rotary switches, are pretty cool. This really deserves a more >>>>> macho knob, but that's all I could find around the place without >>>>> stealing one from something in the antique collection. >>>>> >>>>> The thing it connects to has 13 ARM processors and one FPGA on the >>>>> board. Time warp. >>>>> >>>>> ftp://jjlarkin.lmi.net/V220_top.jpg >>>>> >>>> Do I see three tantalums on the bottom right? Oh-oh ... :-) >>> >>> Yes. LM1117's like tantalums on their outputs; the ESR is just right, >>> and will hold up at -20C. They are all 22u, 10v, 11 cents each, on the >>> outputs of 3.3, 2.5, and 1.25 volt regulators. That should be safe. >>> >>> Why make rules if you can't break them once in a while? >>> >>> The 1.25 is FPGA core voltage; that's an LM1117 with its adj pin >>> grounded. The 2.5 is FPGA VCCaux, another LM1117 with its adj pin tied >>> to the 1.25 rail. I would happily show the programming resistor >>> values, except there aren't any. >>> >> >>Well, if you have good experience with the LM1117 maybe it works. I just >>don't trust LDOs anymore, too much grief. Only one was my own design and >>only because the client absolutely insisted on a particular LDO to be >>used. Then, sure enough ... *PHOOF* ... *POP* > >The 1117 is basically an LM317 architecture with a little less >dropout. The final pass transistor is an NPN, so the open-loop output >impedance is relatively low. They are rugged, cheap, and stable if you >put a tantalum or aluminum on their output. > >I use them as power amps, too, driving the adj pin with an opamp. > >John Yep, 1.2V is not exactly low drop-out. ...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 | Spice is like a sports car... Only as good as the person behind the wheel.
From: Joerg on 25 Jul 2010 20:19
John Larkin wrote: > On Sun, 25 Jul 2010 15:08:52 -0700, Joerg <invalid(a)invalid.invalid> > wrote: > >> John Larkin wrote: >>> On Sun, 25 Jul 2010 14:39:46 -0700, Joerg <invalid(a)invalid.invalid> >>> wrote: >>> >>>> John Larkin wrote: >>>>> I spent most of the day building this. >>>>> >>>>> ftp://jjlarkin.lmi.net/V220_Test_Front.jpg >>>>> >>>>> ftp://jjlarkin.lmi.net/V220_Test_Back.jpg >>>>> >>>>> which is a fixture to help test/cal a new VME module. It's powered by >>>>> a 48-volt wall wart. Those old-fashioned teevee type terminal strips, >>>>> and rotary switches, are pretty cool. This really deserves a more >>>>> macho knob, but that's all I could find around the place without >>>>> stealing one from something in the antique collection. >>>>> >>>>> The thing it connects to has 13 ARM processors and one FPGA on the >>>>> board. Time warp. >>>>> >>>>> ftp://jjlarkin.lmi.net/V220_top.jpg >>>>> >>>> Do I see three tantalums on the bottom right? Oh-oh ... :-) >>> Yes. LM1117's like tantalums on their outputs; the ESR is just right, >>> and will hold up at -20C. They are all 22u, 10v, 11 cents each, on the >>> outputs of 3.3, 2.5, and 1.25 volt regulators. That should be safe. >>> >>> Why make rules if you can't break them once in a while? >>> >>> The 1.25 is FPGA core voltage; that's an LM1117 with its adj pin >>> grounded. The 2.5 is FPGA VCCaux, another LM1117 with its adj pin tied >>> to the 1.25 rail. I would happily show the programming resistor >>> values, except there aren't any. >>> >> Well, if you have good experience with the LM1117 maybe it works. I just >> don't trust LDOs anymore, too much grief. Only one was my own design and >> only because the client absolutely insisted on a particular LDO to be >> used. Then, sure enough ... *PHOOF* ... *POP* > > The 1117 is basically an LM317 architecture with a little less > dropout. The final pass transistor is an NPN, so the open-loop output > impedance is relatively low. They are rugged, cheap, and stable if you > put a tantalum or aluminum on their output. > At least they state a range from 0.3ohms to 22ohms for this one instead of some obscure graph. I'd still prefer ceramics plus resistor but that's more real estate which in your case often matters a lot. > I use them as power amps, too, driving the adj pin with an opamp. > I have done that with the LM317, using it as a modulator. It doesn't get much cheaper than that because the transmit stage needed a regulator anyhow. So it was essentially a free modulator. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. |