A little more data on the 7912. The first plot shows the tempCo of the 7912 measured with ambient temperature swings "7912_TempCo.png". Which is -150 ppm/degC. The second plot is off a 7912 logged for an hour or so, "7912_1PLC.png", nothing too interesting here. However the environmental temperature swing of about 1 degC/hour is pretty conservative for a DUT sitting in free air. Finally, an allan devation plot looking at the normalized stability of a 7912 regulator "7912_AllanDeviation.png". Interestingly here, is, how quick a 15 mK/min temperature swing shoots above the 1/f floor, it's a matter of seconds. Now if your PSRR is 1 ppb/V or better, then all of this is comfortably below the intrinsic noise of a thunderbolt. On Fri, Oct 21, 2016 at 12:20 AM, Scott Stobbe <scott.j.stobbe@gmail.com> wrote: > Nick had mention that the -12V rail on the thunderbolt has the poorest > PSRR with respect to frequency output, so I first took a look at the > venerable 7912. > > The first data-set was taken with a -13.5 VDC input. Attached is the 0.1 > Hz to 10 Hz noise of an essentially quiescently loaded 7912, only a 10k > resistor was added as load for preliminary evaluation. With a 60 dB preamp > the scale of the scope plot is 20 uV/div. The 0.1Hz to 10Hz band noise is > 15 uVrms, which is about 1.3 ppm rms of the DC mean. > > In allan deviation terms, a quiescently loaded 7912 has a spot noise of 7 > uV/rtHz at 1 Hz (on the 1/f slope), normalized that's 580 ppb/rtHz. > Equivalently speaking, the flicker noise floor of an allan deviation plot > would be sqrt(2*ln(2)) that figure to be 6.8E-7. > > Assuming a thunderbolt should be achieving 1/f floor of around 1E-12, it > would need a PSRR of at least 1 ppm/V. I'm sure someone has gone to the > trouble of actually measuring it. > > So from a 0.1 Hz to 10 Hz noise standpoint, the 7912 isn't terrible > with 1.3 ppm rms noise, considering an LM399 is about 0.1 ppm rms, only one > order of magnitude off. > > The bad side of a 7912 is in long-term stability and tempCo, the sample I > tested had at least a 150 ppm/degC tempCo, which is going to put a serious > lump/bump in the 10s tau to gps crossover point on an allan deviation plot. > > > > On Tue, Oct 18, 2016 at 3:05 PM, Scott Stobbe <scott.j.stobbe@gmail.com> > wrote: > >> I'm sure I have some 7805s lying around, maybe a 7812/7912. I'm >> interested to see the 1/f noise of a classic regulator, what load current >> do you expect? I can bias a 7805 for the same load and measure the 0.1 to >> 10 Hz noise. >> >> Also if you have a digital scope without a very good builtin FFT, octave >> would be one solution. >> >> On Tue, Oct 18, 2016 at 10:46 AM, Nick Sayer via time-nuts < >> time-nuts@febo.com> wrote: >> >>> Just an update. I’ve built the second prototype board (I skipped over >>> the first design), and it’s powering my tbolt right now. >>> >>> The design calls for 15v in (though it would also work with 13.8v). The >>> +12 output comes from a D2PAK 7812. For +5, there is an AP1509 buck >>> converter to make around 6.5 volts, then a DPAK 7805. For -12, there is an >>> MC34063 configured as an inverter to make around -13.75 volts and then a >>> DPAK 7912. >>> >>> Steady-state, the system appears to be working just fine. The AP1509’s >>> inductor and the D2PAK 7812 are just warm to the touch. >>> >>> I checked for noise and ripple on the outputs and it’s somewhere around >>> ±2 mV or so generally. From what I can see on the scope, there’s no ripple >>> - it’s all high frequency noise. I am not absolutely certain that the noise >>> measurement represents real noise or the limits of my measuring ability. >>> I’m just using the scope probes the scope came with, and 2 mV/div is its >>> lowest range. >>> >>> I haven’t compared the noise with the ex laptop supply that I was using >>> before, but I’d have to believe it’s cleaner. I don’t really have a way to >>> check the oscillator’s before and after ADEV. My only other reference is an >>> FE5680A, and I think the thunderbolt’s going to be far better at lower tau >>> (where this all matters). >>> >>> I know also that ±2 mV is still one and perhaps two orders of magnitude >>> higher than some have called for. But before I attempt to reduce the noise >>> further, I’d like to know that there are real gains to be had. Would >>> someone with a Thunderbolt and better output noise measuring wherewithal be >>> willing to take a prototype and compare it with something that does have µV >>> levels of noise and ripple so I can get an idea of what there is to gain? >>> If you like, you can make such comparisons public - no secrets here. >>> >>> > On Aug 30, 2016, at 10:37 PM, Nick Sayer <nsayer@kfu.com> wrote: >>> > >>> > >>> >> On Aug 30, 2016, at 8:48 PM, Cube Central <cubecentral@gmail.com> >>> wrote: >>> >> >>> >> I would be interested, I think. Planning ahead for if the one I have >>> for my Thunderbolt fails, I guess. Are there different models or would a >>> photo of the input ports on mine be useful? >>> > >>> > Actually, what I had in mind is to just put a SIP4 header on the board >>> for the output and people could wire the “last mile” themselves. The input >>> is a 2.1mm barrel connector. You use whatever 15W 12VDC wall wart is handy >>> and plug it right in. >>> > >>> > What it really amounts to is that you get +12 volts directly from the >>> input, then there’s a buck converter to drop the +12 down to +5 and an >>> inverter to generate -12 from the +12. Those 3 voltages, plus a ground go >>> to the SIP4. >>> > >>> > So it’s just two switching power supplies to turn a +12 volt only >>> supply into the three-way that the Thunderbolt wants. >>> > >>> > It’d be good for around 1500 mA @ 5V and around 50 mA @ -12 (the +12 >>> spec is whatever is left from the source supply’s power spec) - more than >>> enough for a Thunderbolt. Probably enough for a hard disk or a smallish PC. >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@febo.com >>> To unsubscribe, go to https://www.febo.com/cgi-bin/m >>> ailman/listinfo/time-nuts >>> and follow the instructions there. >>> >> >> >

Hi > On Oct 21, 2016, at 7:44 PM, Scott Stobbe <scott.j.stobbe@gmail.com> wrote: > > A little more data on the 7912. > > The first plot shows the tempCo of the 7912 measured with ambient > temperature swings "7912_TempCo.png". Which is -150 ppm/degC. > > The second plot is off a 7912 logged for an hour or so, "7912_1PLC.png", > nothing too interesting here. However the environmental temperature swing > of about 1 degC/hour is pretty conservative for a DUT sitting in free air. > > Finally, an allan devation plot looking at the normalized stability of a > 7912 regulator "7912_AllanDeviation.png". Interestingly here, is, how quick > a 15 mK/min temperature swing shoots above the 1/f floor, it's a matter of > seconds. > > Now if your PSRR is 1 ppb/V or better, then all of this is comfortably > below the intrinsic noise of a thunderbolt. The main point is that the internal tempco of the TBolt it’s self is much larger than the issues surrounding the power supply pins. The +12 is the only one that is sensitive enough to voltage (change in frequency vs voltage) to contribute to any significant way to the overall stability. Bob > > On Fri, Oct 21, 2016 at 12:20 AM, Scott Stobbe <scott.j.stobbe@gmail.com> > wrote: > >> Nick had mention that the -12V rail on the thunderbolt has the poorest >> PSRR with respect to frequency output, so I first took a look at the >> venerable 7912. >> >> The first data-set was taken with a -13.5 VDC input. Attached is the 0.1 >> Hz to 10 Hz noise of an essentially quiescently loaded 7912, only a 10k >> resistor was added as load for preliminary evaluation. With a 60 dB preamp >> the scale of the scope plot is 20 uV/div. The 0.1Hz to 10Hz band noise is >> 15 uVrms, which is about 1.3 ppm rms of the DC mean. >> >> In allan deviation terms, a quiescently loaded 7912 has a spot noise of 7 >> uV/rtHz at 1 Hz (on the 1/f slope), normalized that's 580 ppb/rtHz. >> Equivalently speaking, the flicker noise floor of an allan deviation plot >> would be sqrt(2*ln(2)) that figure to be 6.8E-7. >> >> Assuming a thunderbolt should be achieving 1/f floor of around 1E-12, it >> would need a PSRR of at least 1 ppm/V. I'm sure someone has gone to the >> trouble of actually measuring it. >> >> So from a 0.1 Hz to 10 Hz noise standpoint, the 7912 isn't terrible >> with 1.3 ppm rms noise, considering an LM399 is about 0.1 ppm rms, only one >> order of magnitude off. >> >> The bad side of a 7912 is in long-term stability and tempCo, the sample I >> tested had at least a 150 ppm/degC tempCo, which is going to put a serious >> lump/bump in the 10s tau to gps crossover point on an allan deviation plot. >> >> >> >> On Tue, Oct 18, 2016 at 3:05 PM, Scott Stobbe <scott.j.stobbe@gmail.com> >> wrote: >> >>> I'm sure I have some 7805s lying around, maybe a 7812/7912. I'm >>> interested to see the 1/f noise of a classic regulator, what load current >>> do you expect? I can bias a 7805 for the same load and measure the 0.1 to >>> 10 Hz noise. >>> >>> Also if you have a digital scope without a very good builtin FFT, octave >>> would be one solution. >>> >>> On Tue, Oct 18, 2016 at 10:46 AM, Nick Sayer via time-nuts < >>> time-nuts@febo.com> wrote: >>> >>>> Just an update. I’ve built the second prototype board (I skipped over >>>> the first design), and it’s powering my tbolt right now. >>>> >>>> The design calls for 15v in (though it would also work with 13.8v). The >>>> +12 output comes from a D2PAK 7812. For +5, there is an AP1509 buck >>>> converter to make around 6.5 volts, then a DPAK 7805. For -12, there is an >>>> MC34063 configured as an inverter to make around -13.75 volts and then a >>>> DPAK 7912. >>>> >>>> Steady-state, the system appears to be working just fine. The AP1509’s >>>> inductor and the D2PAK 7812 are just warm to the touch. >>>> >>>> I checked for noise and ripple on the outputs and it’s somewhere around >>>> ±2 mV or so generally. From what I can see on the scope, there’s no ripple >>>> - it’s all high frequency noise. I am not absolutely certain that the noise >>>> measurement represents real noise or the limits of my measuring ability. >>>> I’m just using the scope probes the scope came with, and 2 mV/div is its >>>> lowest range. >>>> >>>> I haven’t compared the noise with the ex laptop supply that I was using >>>> before, but I’d have to believe it’s cleaner. I don’t really have a way to >>>> check the oscillator’s before and after ADEV. My only other reference is an >>>> FE5680A, and I think the thunderbolt’s going to be far better at lower tau >>>> (where this all matters). >>>> >>>> I know also that ±2 mV is still one and perhaps two orders of magnitude >>>> higher than some have called for. But before I attempt to reduce the noise >>>> further, I’d like to know that there are real gains to be had. Would >>>> someone with a Thunderbolt and better output noise measuring wherewithal be >>>> willing to take a prototype and compare it with something that does have µV >>>> levels of noise and ripple so I can get an idea of what there is to gain? >>>> If you like, you can make such comparisons public - no secrets here. >>>> >>>>> On Aug 30, 2016, at 10:37 PM, Nick Sayer <nsayer@kfu.com> wrote: >>>>> >>>>> >>>>>> On Aug 30, 2016, at 8:48 PM, Cube Central <cubecentral@gmail.com> >>>> wrote: >>>>>> >>>>>> I would be interested, I think. Planning ahead for if the one I have >>>> for my Thunderbolt fails, I guess. Are there different models or would a >>>> photo of the input ports on mine be useful? >>>>> >>>>> Actually, what I had in mind is to just put a SIP4 header on the board >>>> for the output and people could wire the “last mile” themselves. The input >>>> is a 2.1mm barrel connector. You use whatever 15W 12VDC wall wart is handy >>>> and plug it right in. >>>>> >>>>> What it really amounts to is that you get +12 volts directly from the >>>> input, then there’s a buck converter to drop the +12 down to +5 and an >>>> inverter to generate -12 from the +12. Those 3 voltages, plus a ground go >>>> to the SIP4. >>>>> >>>>> So it’s just two switching power supplies to turn a +12 volt only >>>> supply into the three-way that the Thunderbolt wants. >>>>> >>>>> It’d be good for around 1500 mA @ 5V and around 50 mA @ -12 (the +12 >>>> spec is whatever is left from the source supply’s power spec) - more than >>>> enough for a Thunderbolt. Probably enough for a hard disk or a smallish PC. >>>> _______________________________________________ >>>> time-nuts mailing list -- time-nuts@febo.com >>>> To unsubscribe, go to https://www.febo.com/cgi-bin/m >>>> ailman/listinfo/time-nuts >>>> and follow the instructions there. >>>> >>> >>> >> > <7912_1PLC.png><7912_AllanDeviation.png><7912_TempCo.png>_______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.

Interesting, I would have thought that the +12V input would be extremely well regulated since its shared with the oven heater, I*R drops are going to show up every where, if your looking for uV levels of stability. Just a connector has milliohms of contact resistance, let alone routing and cables... On Friday, 21 October 2016, Bob Camp <kb8tq@n1k.org> wrote: > Hi > > > On Oct 21, 2016, at 7:44 PM, Scott Stobbe <scott.j.stobbe@gmail.com > <javascript:;>> wrote: > > > > A little more data on the 7912. > > > > The first plot shows the tempCo of the 7912 measured with ambient > > temperature swings "7912_TempCo.png". Which is -150 ppm/degC. > > > > The second plot is off a 7912 logged for an hour or so, "7912_1PLC.png", > > nothing too interesting here. However the environmental temperature swing > > of about 1 degC/hour is pretty conservative for a DUT sitting in free > air. > > > > Finally, an allan devation plot looking at the normalized stability of a > > 7912 regulator "7912_AllanDeviation.png". Interestingly here, is, how > quick > > a 15 mK/min temperature swing shoots above the 1/f floor, it's a matter > of > > seconds. > > > > Now if your PSRR is 1 ppb/V or better, then all of this is comfortably > > below the intrinsic noise of a thunderbolt. > > The main point is that the internal tempco of the TBolt it’s self is much > larger than > the issues surrounding the power supply pins. The +12 is the only one that > is > sensitive enough to voltage (change in frequency vs voltage) to contribute > to any > significant way to the overall stability. > > Bob > > > > > On Fri, Oct 21, 2016 at 12:20 AM, Scott Stobbe <scott.j.stobbe@gmail.com > <javascript:;>> > > wrote: > > > >> Nick had mention that the -12V rail on the thunderbolt has the poorest > >> PSRR with respect to frequency output, so I first took a look at the > >> venerable 7912. > >> > >> The first data-set was taken with a -13.5 VDC input. Attached is the 0.1 > >> Hz to 10 Hz noise of an essentially quiescently loaded 7912, only a 10k > >> resistor was added as load for preliminary evaluation. With a 60 dB > preamp > >> the scale of the scope plot is 20 uV/div. The 0.1Hz to 10Hz band noise > is > >> 15 uVrms, which is about 1.3 ppm rms of the DC mean. > >> > >> In allan deviation terms, a quiescently loaded 7912 has a spot noise of > 7 > >> uV/rtHz at 1 Hz (on the 1/f slope), normalized that's 580 ppb/rtHz. > >> Equivalently speaking, the flicker noise floor of an allan deviation > plot > >> would be sqrt(2*ln(2)) that figure to be 6.8E-7. > >> > >> Assuming a thunderbolt should be achieving 1/f floor of around 1E-12, it > >> would need a PSRR of at least 1 ppm/V. I'm sure someone has gone to the > >> trouble of actually measuring it. > >> > >> So from a 0.1 Hz to 10 Hz noise standpoint, the 7912 isn't terrible > >> with 1.3 ppm rms noise, considering an LM399 is about 0.1 ppm rms, only > one > >> order of magnitude off. > >> > >> The bad side of a 7912 is in long-term stability and tempCo, the sample > I > >> tested had at least a 150 ppm/degC tempCo, which is going to put a > serious > >> lump/bump in the 10s tau to gps crossover point on an allan deviation > plot. > >> > >> > >> > >> On Tue, Oct 18, 2016 at 3:05 PM, Scott Stobbe <scott.j.stobbe@gmail.com > <javascript:;>> > >> wrote: > >> > >>> I'm sure I have some 7805s lying around, maybe a 7812/7912. I'm > >>> interested to see the 1/f noise of a classic regulator, what load > current > >>> do you expect? I can bias a 7805 for the same load and measure the 0.1 > to > >>> 10 Hz noise. > >>> > >>> Also if you have a digital scope without a very good builtin FFT, > octave > >>> would be one solution. > >>> > >>> On Tue, Oct 18, 2016 at 10:46 AM, Nick Sayer via time-nuts < > >>> time-nuts@febo.com <javascript:;>> wrote: > >>> > >>>> Just an update. I’ve built the second prototype board (I skipped over > >>>> the first design), and it’s powering my tbolt right now. > >>>> > >>>> The design calls for 15v in (though it would also work with 13.8v). > The > >>>> +12 output comes from a D2PAK 7812. For +5, there is an AP1509 buck > >>>> converter to make around 6.5 volts, then a DPAK 7805. For -12, there > is an > >>>> MC34063 configured as an inverter to make around -13.75 volts and > then a > >>>> DPAK 7912. > >>>> > >>>> Steady-state, the system appears to be working just fine. The AP1509’s > >>>> inductor and the D2PAK 7812 are just warm to the touch. > >>>> > >>>> I checked for noise and ripple on the outputs and it’s somewhere > around > >>>> ±2 mV or so generally. From what I can see on the scope, there’s no > ripple > >>>> - it’s all high frequency noise. I am not absolutely certain that the > noise > >>>> measurement represents real noise or the limits of my measuring > ability. > >>>> I’m just using the scope probes the scope came with, and 2 mV/div is > its > >>>> lowest range. > >>>> > >>>> I haven’t compared the noise with the ex laptop supply that I was > using > >>>> before, but I’d have to believe it’s cleaner. I don’t really have a > way to > >>>> check the oscillator’s before and after ADEV. My only other reference > is an > >>>> FE5680A, and I think the thunderbolt’s going to be far better at > lower tau > >>>> (where this all matters). > >>>> > >>>> I know also that ±2 mV is still one and perhaps two orders of > magnitude > >>>> higher than some have called for. But before I attempt to reduce the > noise > >>>> further, I’d like to know that there are real gains to be had. Would > >>>> someone with a Thunderbolt and better output noise measuring > wherewithal be > >>>> willing to take a prototype and compare it with something that does > have µV > >>>> levels of noise and ripple so I can get an idea of what there is to > gain? > >>>> If you like, you can make such comparisons public - no secrets here. > >>>> > >>>>> On Aug 30, 2016, at 10:37 PM, Nick Sayer <nsayer@kfu.com > <javascript:;>> wrote: > >>>>> > >>>>> > >>>>>> On Aug 30, 2016, at 8:48 PM, Cube Central <cubecentral@gmail.com > <javascript:;>> > >>>> wrote: > >>>>>> > >>>>>> I would be interested, I think. Planning ahead for if the one I > have > >>>> for my Thunderbolt fails, I guess. Are there different models or > would a > >>>> photo of the input ports on mine be useful? > >>>>> > >>>>> Actually, what I had in mind is to just put a SIP4 header on the > board > >>>> for the output and people could wire the “last mile” themselves. The > input > >>>> is a 2.1mm barrel connector. You use whatever 15W 12VDC wall wart is > handy > >>>> and plug it right in. > >>>>> > >>>>> What it really amounts to is that you get +12 volts directly from the > >>>> input, then there’s a buck converter to drop the +12 down to +5 and an > >>>> inverter to generate -12 from the +12. Those 3 voltages, plus a > ground go > >>>> to the SIP4. > >>>>> > >>>>> So it’s just two switching power supplies to turn a +12 volt only > >>>> supply into the three-way that the Thunderbolt wants. > >>>>> > >>>>> It’d be good for around 1500 mA @ 5V and around 50 mA @ -12 (the +12 > >>>> spec is whatever is left from the source supply’s power spec) - more > than > >>>> enough for a Thunderbolt. Probably enough for a hard disk or a > smallish PC. > >>>> _______________________________________________ > >>>> time-nuts mailing list -- time-nuts@febo.com <javascript:;> > >>>> To unsubscribe, go to https://www.febo.com/cgi-bin/m > >>>> ailman/listinfo/time-nuts > >>>> and follow the instructions there. > >>>> > >>> > >>> > >> > > <7912_1PLC.png><7912_AllanDeviation.png><7912_ > TempCo.png>_______________________________________________ > > time-nuts mailing list -- time-nuts@febo.com <javascript:;> > > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > > and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com <javascript:;> > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. >

Hi The +12 goes straight to the OCXO. All OCXO’s have a voltage sensitivity. That sensitivity is much higher than voltage sensitivity is much higher than what you see on the other two supply pins. Bob > On Oct 21, 2016, at 11:06 PM, Scott Stobbe <scott.j.stobbe@gmail.com> wrote: > > Interesting, I would have thought that the +12V input would be extremely > well regulated since its shared with the oven heater, I*R drops are going > to show up every where, if your looking for uV levels of stability. > Just a connector has milliohms of contact resistance, let alone routing and > cables... > > On Friday, 21 October 2016, Bob Camp <kb8tq@n1k.org> wrote: > >> Hi >> >>> On Oct 21, 2016, at 7:44 PM, Scott Stobbe <scott.j.stobbe@gmail.com >> <javascript:;>> wrote: >>> >>> A little more data on the 7912. >>> >>> The first plot shows the tempCo of the 7912 measured with ambient >>> temperature swings "7912_TempCo.png". Which is -150 ppm/degC. >>> >>> The second plot is off a 7912 logged for an hour or so, "7912_1PLC.png", >>> nothing too interesting here. However the environmental temperature swing >>> of about 1 degC/hour is pretty conservative for a DUT sitting in free >> air. >>> >>> Finally, an allan devation plot looking at the normalized stability of a >>> 7912 regulator "7912_AllanDeviation.png". Interestingly here, is, how >> quick >>> a 15 mK/min temperature swing shoots above the 1/f floor, it's a matter >> of >>> seconds. >>> >>> Now if your PSRR is 1 ppb/V or better, then all of this is comfortably >>> below the intrinsic noise of a thunderbolt. >> >> The main point is that the internal tempco of the TBolt it’s self is much >> larger than >> the issues surrounding the power supply pins. The +12 is the only one that >> is >> sensitive enough to voltage (change in frequency vs voltage) to contribute >> to any >> significant way to the overall stability. >> >> Bob >> >>> >>> On Fri, Oct 21, 2016 at 12:20 AM, Scott Stobbe <scott.j.stobbe@gmail.com >> <javascript:;>> >>> wrote: >>> >>>> Nick had mention that the -12V rail on the thunderbolt has the poorest >>>> PSRR with respect to frequency output, so I first took a look at the >>>> venerable 7912. >>>> >>>> The first data-set was taken with a -13.5 VDC input. Attached is the 0.1 >>>> Hz to 10 Hz noise of an essentially quiescently loaded 7912, only a 10k >>>> resistor was added as load for preliminary evaluation. With a 60 dB >> preamp >>>> the scale of the scope plot is 20 uV/div. The 0.1Hz to 10Hz band noise >> is >>>> 15 uVrms, which is about 1.3 ppm rms of the DC mean. >>>> >>>> In allan deviation terms, a quiescently loaded 7912 has a spot noise of >> 7 >>>> uV/rtHz at 1 Hz (on the 1/f slope), normalized that's 580 ppb/rtHz. >>>> Equivalently speaking, the flicker noise floor of an allan deviation >> plot >>>> would be sqrt(2*ln(2)) that figure to be 6.8E-7. >>>> >>>> Assuming a thunderbolt should be achieving 1/f floor of around 1E-12, it >>>> would need a PSRR of at least 1 ppm/V. I'm sure someone has gone to the >>>> trouble of actually measuring it. >>>> >>>> So from a 0.1 Hz to 10 Hz noise standpoint, the 7912 isn't terrible >>>> with 1.3 ppm rms noise, considering an LM399 is about 0.1 ppm rms, only >> one >>>> order of magnitude off. >>>> >>>> The bad side of a 7912 is in long-term stability and tempCo, the sample >> I >>>> tested had at least a 150 ppm/degC tempCo, which is going to put a >> serious >>>> lump/bump in the 10s tau to gps crossover point on an allan deviation >> plot. >>>> >>>> >>>> >>>> On Tue, Oct 18, 2016 at 3:05 PM, Scott Stobbe <scott.j.stobbe@gmail.com >> <javascript:;>> >>>> wrote: >>>> >>>>> I'm sure I have some 7805s lying around, maybe a 7812/7912. I'm >>>>> interested to see the 1/f noise of a classic regulator, what load >> current >>>>> do you expect? I can bias a 7805 for the same load and measure the 0.1 >> to >>>>> 10 Hz noise. >>>>> >>>>> Also if you have a digital scope without a very good builtin FFT, >> octave >>>>> would be one solution. >>>>> >>>>> On Tue, Oct 18, 2016 at 10:46 AM, Nick Sayer via time-nuts < >>>>> time-nuts@febo.com <javascript:;>> wrote: >>>>> >>>>>> Just an update. I’ve built the second prototype board (I skipped over >>>>>> the first design), and it’s powering my tbolt right now. >>>>>> >>>>>> The design calls for 15v in (though it would also work with 13.8v). >> The >>>>>> +12 output comes from a D2PAK 7812. For +5, there is an AP1509 buck >>>>>> converter to make around 6.5 volts, then a DPAK 7805. For -12, there >> is an >>>>>> MC34063 configured as an inverter to make around -13.75 volts and >> then a >>>>>> DPAK 7912. >>>>>> >>>>>> Steady-state, the system appears to be working just fine. The AP1509’s >>>>>> inductor and the D2PAK 7812 are just warm to the touch. >>>>>> >>>>>> I checked for noise and ripple on the outputs and it’s somewhere >> around >>>>>> ±2 mV or so generally. From what I can see on the scope, there’s no >> ripple >>>>>> - it’s all high frequency noise. I am not absolutely certain that the >> noise >>>>>> measurement represents real noise or the limits of my measuring >> ability. >>>>>> I’m just using the scope probes the scope came with, and 2 mV/div is >> its >>>>>> lowest range. >>>>>> >>>>>> I haven’t compared the noise with the ex laptop supply that I was >> using >>>>>> before, but I’d have to believe it’s cleaner. I don’t really have a >> way to >>>>>> check the oscillator’s before and after ADEV. My only other reference >> is an >>>>>> FE5680A, and I think the thunderbolt’s going to be far better at >> lower tau >>>>>> (where this all matters). >>>>>> >>>>>> I know also that ±2 mV is still one and perhaps two orders of >> magnitude >>>>>> higher than some have called for. But before I attempt to reduce the >> noise >>>>>> further, I’d like to know that there are real gains to be had. Would >>>>>> someone with a Thunderbolt and better output noise measuring >> wherewithal be >>>>>> willing to take a prototype and compare it with something that does >> have µV >>>>>> levels of noise and ripple so I can get an idea of what there is to >> gain? >>>>>> If you like, you can make such comparisons public - no secrets here. >>>>>> >>>>>>> On Aug 30, 2016, at 10:37 PM, Nick Sayer <nsayer@kfu.com >> <javascript:;>> wrote: >>>>>>> >>>>>>> >>>>>>>> On Aug 30, 2016, at 8:48 PM, Cube Central <cubecentral@gmail.com >> <javascript:;>> >>>>>> wrote: >>>>>>>> >>>>>>>> I would be interested, I think. Planning ahead for if the one I >> have >>>>>> for my Thunderbolt fails, I guess. Are there different models or >> would a >>>>>> photo of the input ports on mine be useful? >>>>>>> >>>>>>> Actually, what I had in mind is to just put a SIP4 header on the >> board >>>>>> for the output and people could wire the “last mile” themselves. The >> input >>>>>> is a 2.1mm barrel connector. You use whatever 15W 12VDC wall wart is >> handy >>>>>> and plug it right in. >>>>>>> >>>>>>> What it really amounts to is that you get +12 volts directly from the >>>>>> input, then there’s a buck converter to drop the +12 down to +5 and an >>>>>> inverter to generate -12 from the +12. Those 3 voltages, plus a >> ground go >>>>>> to the SIP4. >>>>>>> >>>>>>> So it’s just two switching power supplies to turn a +12 volt only >>>>>> supply into the three-way that the Thunderbolt wants. >>>>>>> >>>>>>> It’d be good for around 1500 mA @ 5V and around 50 mA @ -12 (the +12 >>>>>> spec is whatever is left from the source supply’s power spec) - more >> than >>>>>> enough for a Thunderbolt. Probably enough for a hard disk or a >> smallish PC. >>>>>> _______________________________________________ >>>>>> time-nuts mailing list -- time-nuts@febo.com <javascript:;> >>>>>> To unsubscribe, go to https://www.febo.com/cgi-bin/m >>>>>> ailman/listinfo/time-nuts >>>>>> and follow the instructions there. >>>>>> >>>>> >>>>> >>>> >>> <7912_1PLC.png><7912_AllanDeviation.png><7912_ >> TempCo.png>_______________________________________________ >>> time-nuts mailing list -- time-nuts@febo.com <javascript:;> >>> To unsubscribe, go to https://www.febo.com/cgi-bin/ >> mailman/listinfo/time-nuts >>> and follow the instructions there. >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com <javascript:;> >> To unsubscribe, go to https://www.febo.com/cgi-bin/ >> mailman/listinfo/time-nuts >> and follow the instructions there. >> > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.

It all depends what the -12V rail is for, some have said it directly references the EFC dac. I would hope an ocxo would have a better tuning gain on its efc pin than supply pin but maybe that's not always true. On Saturday, 22 October 2016, Bob Camp <kb8tq@n1k.org> wrote: > Hi > > The +12 goes straight to the OCXO. All OCXO’s have a voltage sensitivity. > That sensitivity is much higher than voltage sensitivity is much higher > than > what you see on the other two supply pins. > > Bob > > > On Oct 21, 2016, at 11:06 PM, Scott Stobbe <scott.j.stobbe@gmail.com > <javascript:;>> wrote: > > > > Interesting, I would have thought that the +12V input would be extremely > > well regulated since its shared with the oven heater, I*R drops are going > > to show up every where, if your looking for uV levels of stability. > > Just a connector has milliohms of contact resistance, let alone routing > and > > cables... > > > > On Friday, 21 October 2016, Bob Camp <kb8tq@n1k.org <javascript:;>> > wrote: > > > >> Hi > >> > >>> On Oct 21, 2016, at 7:44 PM, Scott Stobbe <scott.j.stobbe@gmail.com > <javascript:;> > >> <javascript:;>> wrote: > >>> > >>> A little more data on the 7912. > >>> > >>> The first plot shows the tempCo of the 7912 measured with ambient > >>> temperature swings "7912_TempCo.png". Which is -150 ppm/degC. > >>> > >>> The second plot is off a 7912 logged for an hour or so, > "7912_1PLC.png", > >>> nothing too interesting here. However the environmental temperature > swing > >>> of about 1 degC/hour is pretty conservative for a DUT sitting in free > >> air. > >>> > >>> Finally, an allan devation plot looking at the normalized stability of > a > >>> 7912 regulator "7912_AllanDeviation.png". Interestingly here, is, how > >> quick > >>> a 15 mK/min temperature swing shoots above the 1/f floor, it's a matter > >> of > >>> seconds. > >>> > >>> Now if your PSRR is 1 ppb/V or better, then all of this is comfortably > >>> below the intrinsic noise of a thunderbolt. > >> > >> The main point is that the internal tempco of the TBolt it’s self is > much > >> larger than > >> the issues surrounding the power supply pins. The +12 is the only one > that > >> is > >> sensitive enough to voltage (change in frequency vs voltage) to > contribute > >> to any > >> significant way to the overall stability. > >> > >> Bob > >> > >>> > >>> On Fri, Oct 21, 2016 at 12:20 AM, Scott Stobbe < > scott.j.stobbe@gmail.com <javascript:;> > >> <javascript:;>> > >>> wrote: > >>> > >>>> Nick had mention that the -12V rail on the thunderbolt has the poorest > >>>> PSRR with respect to frequency output, so I first took a look at the > >>>> venerable 7912. > >>>> > >>>> The first data-set was taken with a -13.5 VDC input. Attached is the > 0.1 > >>>> Hz to 10 Hz noise of an essentially quiescently loaded 7912, only a > 10k > >>>> resistor was added as load for preliminary evaluation. With a 60 dB > >> preamp > >>>> the scale of the scope plot is 20 uV/div. The 0.1Hz to 10Hz band noise > >> is > >>>> 15 uVrms, which is about 1.3 ppm rms of the DC mean. > >>>> > >>>> In allan deviation terms, a quiescently loaded 7912 has a spot noise > of > >> 7 > >>>> uV/rtHz at 1 Hz (on the 1/f slope), normalized that's 580 ppb/rtHz. > >>>> Equivalently speaking, the flicker noise floor of an allan deviation > >> plot > >>>> would be sqrt(2*ln(2)) that figure to be 6.8E-7. > >>>> > >>>> Assuming a thunderbolt should be achieving 1/f floor of around 1E-12, > it > >>>> would need a PSRR of at least 1 ppm/V. I'm sure someone has gone to > the > >>>> trouble of actually measuring it. > >>>> > >>>> So from a 0.1 Hz to 10 Hz noise standpoint, the 7912 isn't terrible > >>>> with 1.3 ppm rms noise, considering an LM399 is about 0.1 ppm rms, > only > >> one > >>>> order of magnitude off. > >>>> > >>>> The bad side of a 7912 is in long-term stability and tempCo, the > sample > >> I > >>>> tested had at least a 150 ppm/degC tempCo, which is going to put a > >> serious > >>>> lump/bump in the 10s tau to gps crossover point on an allan deviation > >> plot. > >>>> > >>>> > >>>> > >>>> On Tue, Oct 18, 2016 at 3:05 PM, Scott Stobbe < > scott.j.stobbe@gmail.com <javascript:;> > >> <javascript:;>> > >>>> wrote: > >>>> > >>>>> I'm sure I have some 7805s lying around, maybe a 7812/7912. I'm > >>>>> interested to see the 1/f noise of a classic regulator, what load > >> current > >>>>> do you expect? I can bias a 7805 for the same load and measure the > 0.1 > >> to > >>>>> 10 Hz noise. > >>>>> > >>>>> Also if you have a digital scope without a very good builtin FFT, > >> octave > >>>>> would be one solution. > >>>>> > >>>>> On Tue, Oct 18, 2016 at 10:46 AM, Nick Sayer via time-nuts < > >>>>> time-nuts@febo.com <javascript:;> <javascript:;>> wrote: > >>>>> > >>>>>> Just an update. I’ve built the second prototype board (I skipped > over > >>>>>> the first design), and it’s powering my tbolt right now. > >>>>>> > >>>>>> The design calls for 15v in (though it would also work with 13.8v). > >> The > >>>>>> +12 output comes from a D2PAK 7812. For +5, there is an AP1509 buck > >>>>>> converter to make around 6.5 volts, then a DPAK 7805. For -12, there > >> is an > >>>>>> MC34063 configured as an inverter to make around -13.75 volts and > >> then a > >>>>>> DPAK 7912. > >>>>>> > >>>>>> Steady-state, the system appears to be working just fine. The > AP1509’s > >>>>>> inductor and the D2PAK 7812 are just warm to the touch. > >>>>>> > >>>>>> I checked for noise and ripple on the outputs and it’s somewhere > >> around > >>>>>> ±2 mV or so generally. From what I can see on the scope, there’s no > >> ripple > >>>>>> - it’s all high frequency noise. I am not absolutely certain that > the > >> noise > >>>>>> measurement represents real noise or the limits of my measuring > >> ability. > >>>>>> I’m just using the scope probes the scope came with, and 2 mV/div is > >> its > >>>>>> lowest range. > >>>>>> > >>>>>> I haven’t compared the noise with the ex laptop supply that I was > >> using > >>>>>> before, but I’d have to believe it’s cleaner. I don’t really have a > >> way to > >>>>>> check the oscillator’s before and after ADEV. My only other > reference > >> is an > >>>>>> FE5680A, and I think the thunderbolt’s going to be far better at > >> lower tau > >>>>>> (where this all matters). > >>>>>> > >>>>>> I know also that ±2 mV is still one and perhaps two orders of > >> magnitude > >>>>>> higher than some have called for. But before I attempt to reduce the > >> noise > >>>>>> further, I’d like to know that there are real gains to be had. Would > >>>>>> someone with a Thunderbolt and better output noise measuring > >> wherewithal be > >>>>>> willing to take a prototype and compare it with something that does > >> have µV > >>>>>> levels of noise and ripple so I can get an idea of what there is to > >> gain? > >>>>>> If you like, you can make such comparisons public - no secrets here. > >>>>>> > >>>>>>> On Aug 30, 2016, at 10:37 PM, Nick Sayer <nsayer@kfu.com > <javascript:;> > >> <javascript:;>> wrote: > >>>>>>> > >>>>>>> > >>>>>>>> On Aug 30, 2016, at 8:48 PM, Cube Central <cubecentral@gmail.com > <javascript:;> > >> <javascript:;>> > >>>>>> wrote: > >>>>>>>> > >>>>>>>> I would be interested, I think. Planning ahead for if the one I > >> have > >>>>>> for my Thunderbolt fails, I guess. Are there different models or > >> would a > >>>>>> photo of the input ports on mine be useful? > >>>>>>> > >>>>>>> Actually, what I had in mind is to just put a SIP4 header on the > >> board > >>>>>> for the output and people could wire the “last mile” themselves. The > >> input > >>>>>> is a 2.1mm barrel connector. You use whatever 15W 12VDC wall wart is > >> handy > >>>>>> and plug it right in. > >>>>>>> > >>>>>>> What it really amounts to is that you get +12 volts directly from > the > >>>>>> input, then there’s a buck converter to drop the +12 down to +5 and > an > >>>>>> inverter to generate -12 from the +12. Those 3 voltages, plus a > >> ground go > >>>>>> to the SIP4. > >>>>>>> > >>>>>>> So it’s just two switching power supplies to turn a +12 volt only > >>>>>> supply into the three-way that the Thunderbolt wants. > >>>>>>> > >>>>>>> It’d be good for around 1500 mA @ 5V and around 50 mA @ -12 (the > +12 > >>>>>> spec is whatever is left from the source supply’s power spec) - more > >> than > >>>>>> enough for a Thunderbolt. Probably enough for a hard disk or a > >> smallish PC. > >>>>>> _______________________________________________ > >>>>>> time-nuts mailing list -- time-nuts@febo.com <javascript:;> > <javascript:;> > >>>>>> To unsubscribe, go to https://www.febo.com/cgi-bin/m > >>>>>> ailman/listinfo/time-nuts > >>>>>> and follow the instructions there. > >>>>>> > >>>>> > >>>>> > >>>> > >>> <7912_1PLC.png><7912_AllanDeviation.png><7912_ > >> TempCo.png>_______________________________________________ > >>> time-nuts mailing list -- time-nuts@febo.com <javascript:;> > <javascript:;> > >>> To unsubscribe, go to https://www.febo.com/cgi-bin/ > >> mailman/listinfo/time-nuts > >>> and follow the instructions there. > >> > >> _______________________________________________ > >> time-nuts mailing list -- time-nuts@febo.com <javascript:;> > <javascript:;> > >> To unsubscribe, go to https://www.febo.com/cgi-bin/ > >> mailman/listinfo/time-nuts > >> and follow the instructions there. > >> > > _______________________________________________ > > time-nuts mailing list -- time-nuts@febo.com <javascript:;> > > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > > and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com <javascript:;> > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. >

Hi The -12 V line is not the reference for the EFC. It *is* one supply into the op amp circuit that drives the EFC. Since the EFC is +/- 5V, there must be both a positive and a negative supply into the driver circuit for full output swing. The -12 can be anything between about -13 and -7 without significantly impacting the function of the device. In fact, people with EFC voltages that are slightly positive have accidentally proven that the TBolt will work (lock up and function correctly) with zero volts on the -12V line. Bob > On Oct 22, 2016, at 10:24 AM, Scott Stobbe <scott.j.stobbe@gmail.com> wrote: > > It all depends what the -12V rail is for, some have said it directly > references the EFC dac. I would hope an ocxo would have a better tuning > gain on its efc pin than supply pin but maybe that's not always true. > > On Saturday, 22 October 2016, Bob Camp <kb8tq@n1k.org> wrote: > >> Hi >> >> The +12 goes straight to the OCXO. All OCXO’s have a voltage sensitivity. >> That sensitivity is much higher than voltage sensitivity is much higher >> than >> what you see on the other two supply pins. >> >> Bob >> >>> On Oct 21, 2016, at 11:06 PM, Scott Stobbe <scott.j.stobbe@gmail.com >> <javascript:;>> wrote: >>> >>> Interesting, I would have thought that the +12V input would be extremely >>> well regulated since its shared with the oven heater, I*R drops are going >>> to show up every where, if your looking for uV levels of stability. >>> Just a connector has milliohms of contact resistance, let alone routing >> and >>> cables... >>> >>> On Friday, 21 October 2016, Bob Camp <kb8tq@n1k.org <javascript:;>> >> wrote: >>> >>>> Hi >>>> >>>>> On Oct 21, 2016, at 7:44 PM, Scott Stobbe <scott.j.stobbe@gmail.com >> <javascript:;> >>>> <javascript:;>> wrote: >>>>> >>>>> A little more data on the 7912. >>>>> >>>>> The first plot shows the tempCo of the 7912 measured with ambient >>>>> temperature swings "7912_TempCo.png". Which is -150 ppm/degC. >>>>> >>>>> The second plot is off a 7912 logged for an hour or so, >> "7912_1PLC.png", >>>>> nothing too interesting here. However the environmental temperature >> swing >>>>> of about 1 degC/hour is pretty conservative for a DUT sitting in free >>>> air. >>>>> >>>>> Finally, an allan devation plot looking at the normalized stability of >> a >>>>> 7912 regulator "7912_AllanDeviation.png". Interestingly here, is, how >>>> quick >>>>> a 15 mK/min temperature swing shoots above the 1/f floor, it's a matter >>>> of >>>>> seconds. >>>>> >>>>> Now if your PSRR is 1 ppb/V or better, then all of this is comfortably >>>>> below the intrinsic noise of a thunderbolt. >>>> >>>> The main point is that the internal tempco of the TBolt it’s self is >> much >>>> larger than >>>> the issues surrounding the power supply pins. The +12 is the only one >> that >>>> is >>>> sensitive enough to voltage (change in frequency vs voltage) to >> contribute >>>> to any >>>> significant way to the overall stability. >>>> >>>> Bob >>>> >>>>> >>>>> On Fri, Oct 21, 2016 at 12:20 AM, Scott Stobbe < >> scott.j.stobbe@gmail.com <javascript:;> >>>> <javascript:;>> >>>>> wrote: >>>>> >>>>>> Nick had mention that the -12V rail on the thunderbolt has the poorest >>>>>> PSRR with respect to frequency output, so I first took a look at the >>>>>> venerable 7912. >>>>>> >>>>>> The first data-set was taken with a -13.5 VDC input. Attached is the >> 0.1 >>>>>> Hz to 10 Hz noise of an essentially quiescently loaded 7912, only a >> 10k >>>>>> resistor was added as load for preliminary evaluation. With a 60 dB >>>> preamp >>>>>> the scale of the scope plot is 20 uV/div. The 0.1Hz to 10Hz band noise >>>> is >>>>>> 15 uVrms, which is about 1.3 ppm rms of the DC mean. >>>>>> >>>>>> In allan deviation terms, a quiescently loaded 7912 has a spot noise >> of >>>> 7 >>>>>> uV/rtHz at 1 Hz (on the 1/f slope), normalized that's 580 ppb/rtHz. >>>>>> Equivalently speaking, the flicker noise floor of an allan deviation >>>> plot >>>>>> would be sqrt(2*ln(2)) that figure to be 6.8E-7. >>>>>> >>>>>> Assuming a thunderbolt should be achieving 1/f floor of around 1E-12, >> it >>>>>> would need a PSRR of at least 1 ppm/V. I'm sure someone has gone to >> the >>>>>> trouble of actually measuring it. >>>>>> >>>>>> So from a 0.1 Hz to 10 Hz noise standpoint, the 7912 isn't terrible >>>>>> with 1.3 ppm rms noise, considering an LM399 is about 0.1 ppm rms, >> only >>>> one >>>>>> order of magnitude off. >>>>>> >>>>>> The bad side of a 7912 is in long-term stability and tempCo, the >> sample >>>> I >>>>>> tested had at least a 150 ppm/degC tempCo, which is going to put a >>>> serious >>>>>> lump/bump in the 10s tau to gps crossover point on an allan deviation >>>> plot. >>>>>> >>>>>> >>>>>> >>>>>> On Tue, Oct 18, 2016 at 3:05 PM, Scott Stobbe < >> scott.j.stobbe@gmail.com <javascript:;> >>>> <javascript:;>> >>>>>> wrote: >>>>>> >>>>>>> I'm sure I have some 7805s lying around, maybe a 7812/7912. I'm >>>>>>> interested to see the 1/f noise of a classic regulator, what load >>>> current >>>>>>> do you expect? I can bias a 7805 for the same load and measure the >> 0.1 >>>> to >>>>>>> 10 Hz noise. >>>>>>> >>>>>>> Also if you have a digital scope without a very good builtin FFT, >>>> octave >>>>>>> would be one solution. >>>>>>> >>>>>>> On Tue, Oct 18, 2016 at 10:46 AM, Nick Sayer via time-nuts < >>>>>>> time-nuts@febo.com <javascript:;> <javascript:;>> wrote: >>>>>>> >>>>>>>> Just an update. I’ve built the second prototype board (I skipped >> over >>>>>>>> the first design), and it’s powering my tbolt right now. >>>>>>>> >>>>>>>> The design calls for 15v in (though it would also work with 13.8v). >>>> The >>>>>>>> +12 output comes from a D2PAK 7812. For +5, there is an AP1509 buck >>>>>>>> converter to make around 6.5 volts, then a DPAK 7805. For -12, there >>>> is an >>>>>>>> MC34063 configured as an inverter to make around -13.75 volts and >>>> then a >>>>>>>> DPAK 7912. >>>>>>>> >>>>>>>> Steady-state, the system appears to be working just fine. The >> AP1509’s >>>>>>>> inductor and the D2PAK 7812 are just warm to the touch. >>>>>>>> >>>>>>>> I checked for noise and ripple on the outputs and it’s somewhere >>>> around >>>>>>>> ±2 mV or so generally. From what I can see on the scope, there’s no >>>> ripple >>>>>>>> - it’s all high frequency noise. I am not absolutely certain that >> the >>>> noise >>>>>>>> measurement represents real noise or the limits of my measuring >>>> ability. >>>>>>>> I’m just using the scope probes the scope came with, and 2 mV/div is >>>> its >>>>>>>> lowest range. >>>>>>>> >>>>>>>> I haven’t compared the noise with the ex laptop supply that I was >>>> using >>>>>>>> before, but I’d have to believe it’s cleaner. I don’t really have a >>>> way to >>>>>>>> check the oscillator’s before and after ADEV. My only other >> reference >>>> is an >>>>>>>> FE5680A, and I think the thunderbolt’s going to be far better at >>>> lower tau >>>>>>>> (where this all matters). >>>>>>>> >>>>>>>> I know also that ±2 mV is still one and perhaps two orders of >>>> magnitude >>>>>>>> higher than some have called for. But before I attempt to reduce the >>>> noise >>>>>>>> further, I’d like to know that there are real gains to be had. Would >>>>>>>> someone with a Thunderbolt and better output noise measuring >>>> wherewithal be >>>>>>>> willing to take a prototype and compare it with something that does >>>> have µV >>>>>>>> levels of noise and ripple so I can get an idea of what there is to >>>> gain? >>>>>>>> If you like, you can make such comparisons public - no secrets here. >>>>>>>> >>>>>>>>> On Aug 30, 2016, at 10:37 PM, Nick Sayer <nsayer@kfu.com >> <javascript:;> >>>> <javascript:;>> wrote: >>>>>>>>> >>>>>>>>> >>>>>>>>>> On Aug 30, 2016, at 8:48 PM, Cube Central <cubecentral@gmail.com >> <javascript:;> >>>> <javascript:;>> >>>>>>>> wrote: >>>>>>>>>> >>>>>>>>>> I would be interested, I think. Planning ahead for if the one I >>>> have >>>>>>>> for my Thunderbolt fails, I guess. Are there different models or >>>> would a >>>>>>>> photo of the input ports on mine be useful? >>>>>>>>> >>>>>>>>> Actually, what I had in mind is to just put a SIP4 header on the >>>> board >>>>>>>> for the output and people could wire the “last mile” themselves. The >>>> input >>>>>>>> is a 2.1mm barrel connector. You use whatever 15W 12VDC wall wart is >>>> handy >>>>>>>> and plug it right in. >>>>>>>>> >>>>>>>>> What it really amounts to is that you get +12 volts directly from >> the >>>>>>>> input, then there’s a buck converter to drop the +12 down to +5 and >> an >>>>>>>> inverter to generate -12 from the +12. Those 3 voltages, plus a >>>> ground go >>>>>>>> to the SIP4. >>>>>>>>> >>>>>>>>> So it’s just two switching power supplies to turn a +12 volt only >>>>>>>> supply into the three-way that the Thunderbolt wants. >>>>>>>>> >>>>>>>>> It’d be good for around 1500 mA @ 5V and around 50 mA @ -12 (the >> +12 >>>>>>>> spec is whatever is left from the source supply’s power spec) - more >>>> than >>>>>>>> enough for a Thunderbolt. Probably enough for a hard disk or a >>>> smallish PC. >>>>>>>> _______________________________________________ >>>>>>>> time-nuts mailing list -- time-nuts@febo.com <javascript:;> >> <javascript:;> >>>>>>>> To unsubscribe, go to https://www.febo.com/cgi-bin/m >>>>>>>> ailman/listinfo/time-nuts >>>>>>>> and follow the instructions there. >>>>>>>> >>>>>>> >>>>>>> >>>>>> >>>>> <7912_1PLC.png><7912_AllanDeviation.png><7912_ >>>> TempCo.png>_______________________________________________ >>>>> time-nuts mailing list -- time-nuts@febo.com <javascript:;> >> <javascript:;> >>>>> To unsubscribe, go to https://www.febo.com/cgi-bin/ >>>> mailman/listinfo/time-nuts >>>>> and follow the instructions there. >>>> >>>> _______________________________________________ >>>> time-nuts mailing list -- time-nuts@febo.com <javascript:;> >> <javascript:;> >>>> To unsubscribe, go to https://www.febo.com/cgi-bin/ >>>> mailman/listinfo/time-nuts >>>> and follow the instructions there. >>>> >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@febo.com <javascript:;> >>> To unsubscribe, go to https://www.febo.com/cgi-bin/ >> mailman/listinfo/time-nuts >>> and follow the instructions there. >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com <javascript:;> >> To unsubscribe, go to https://www.febo.com/cgi-bin/ >> mailman/listinfo/time-nuts >> and follow the instructions there. >> > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.