On Wed, 18 Feb 2026 22:12:12 -0000 (UTC), Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
Is generally the pits.
Anybody got a fave negative regulator with decent PSR? I need a few rails >> at no more than 150 mA, and the landscape is bleak.
The 337-style ones seem to rule the roost, and they stink.
IrCOm thinking of using TCA0372s, but they donrCOt have a PSR spec at all. >>
Cheers
Phil Hobbs
TPS723xx claims ultra low noise and high PSRR.
I like to put an RC at the input of a lin reg. That improves hf psrr,
shares some power dissipation, and gives me a way to measure the
current.
I like to bypass the top resistor in a feedback divider too.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
On 2/18/26 2:12 PM, Phil Hobbs wrote:
Is generally the pits.
Anybody got a fave negative regulator with decent PSR?-a I need a few
rails
at no more than 150 mA, and the landscape is bleak.
The 337-style ones seem to rule the roost, and they stink.
IrCOm thinking of using TCA0372s, but they donrCOt have a PSR spec at all. >>
I don't know the voltage ranges you need but Analog Devices usually
makes quality stuff:
https://www.analog.com/media/en/technical-documentation/data-sheets/ADP7183.pdf
Expensive, of course, so I haven't used them myself yet.
On Wed, 18 Feb 2026 22:12:12 -0000 (UTC), Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
Is generally the pits.
Anybody got a fave negative regulator with decent PSR? I need a few rails >> at no more than 150 mA, and the landscape is bleak.
The 337-style ones seem to rule the roost, and they stink.
IrCOm thinking of using TCA0372s, but they donrCOt have a PSR spec at all.
LT3094 (LT3045).
On 2026-02-18 22:34, john larkin wrote:
On Wed, 18 Feb 2026 22:12:12 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
Is generally the pits.
Anybody got a fave negative regulator with decent PSR? I need a few rails >>> at no more than 150 mA, and the landscape is bleak.
The 337-style ones seem to rule the roost, and they stink.
IAm thinking of using TCA0372s, but they donAt have a PSR spec at all.
Cheers
Phil Hobbs
TPS723xx claims ultra low noise and high PSRR.
I like to put an RC at the input of a lin reg. That improves hf psrr,
shares some power dissipation, and gives me a way to measure the
current.
I like to bypass the top resistor in a feedback divider too.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
About 20 dB at 10 kHz. :( They're almost all like that.
I've got a four-pole RLC LPF on each input that's -3 dB at 12 kHz and >(theoretically) -100 dB at 300 kHz, before veering off into spherical >meadows of -150 to -220 dB from 1 to 50 MHz. ;) Simulation shows no >peaking and no overshoot.
1 ohm 2 ohm 47u
Supply 0---POLYSWITCH--*--RRRR--*--LLLLLL---*--0 --> vregs
| | |
4.7 uF (about CCC CCC 4.7uF CCC
3.3 @ 15V) CCC CCC CCC 2x 4.7uF
| | |
GND GND GND
The caps are all CL31B475KAHNNNE (1206, X7R, 5 cents) and the inductor
is ANR6045T470M (6mm x 6mm, 0.25 ohm ESR, also 5 cents). I'm splurging
on the polyswitch (RXEF030, about 12 cents). That's seven parts on each >polarity, amortized over all the rails, not counting the RF bypass cap
and TVS (SMBJ15A, about 8 cents).
The regulators typically have 50 dB-ish rejection near DC, some
considerably less, but then go into the tank above 1 kHz or so, like
20-25 dB at 10 kHz. (Lasse's one is about 20 dB better there, for an
extra buck per rail). Discrete front ends have no PSR to speak of, so I >really need > 60 dB from hum frequencies to 10 kHz, and much better
above there.
So it's looking like a cap multiplier supervised by an LM4041 shunt >reference as the next stage. That's about a dozen parts per rail, which >isn't brilliant. It's hard to share them, because two of the rails need
to be near the negative input supply.
Humph.
Cheers
Phil Hobbs
On 2026-02-18 20:41, JM wrote:
On Wed, 18 Feb 2026 22:12:12 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
Is generally the pits.LT3094 (LT3045).
Anybody got a fave negative regulator with decent PSR?-a I need a few
rails
at no more than 150 mA, and the landscape is bleak.
The 337-style ones seem to rule the roost, and they stink.
IrCOm thinking of using TCA0372s, but they donrCOt have a PSR spec at all. >>
That's a very nice part, which would be perfect if it didn't cost $6 per rail. :(
On Thu, 19 Feb 2026 13:50:52 -0500, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2026-02-18 22:34, john larkin wrote:
On Wed, 18 Feb 2026 22:12:12 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
Is generally the pits.
Anybody got a fave negative regulator with decent PSR? I need a few rails >>>> at no more than 150 mA, and the landscape is bleak.
The 337-style ones seem to rule the roost, and they stink.
IrCOm thinking of using TCA0372s, but they donrCOt have a PSR spec at all. >>>>
Cheers
Phil Hobbs
TPS723xx claims ultra low noise and high PSRR.
I like to put an RC at the input of a lin reg. That improves hf psrr,
shares some power dissipation, and gives me a way to measure the
current.
I like to bypass the top resistor in a feedback divider too.
About 20 dB at 10 kHz. :( They're almost all like that.
I guess that the substrate is the unreg input on a negative regulator,
so it couples into everything.
I've got a four-pole RLC LPF on each input that's -3 dB at 12 kHz and
(theoretically) -100 dB at 300 kHz, before veering off into spherical
meadows of -150 to -220 dB from 1 to 50 MHz. ;) Simulation shows no
peaking and no overshoot.
1 ohm 2 ohm 47u
Supply 0---POLYSWITCH--*--RRRR--*--LLLLLL---*--0 --> vregs
| | |
4.7 uF (about CCC CCC 4.7uF CCC
3.3 @ 15V) CCC CCC CCC 2x 4.7uF
| | |
GND GND GND
Maybe get some 150 uF polymer caps?
The caps are all CL31B475KAHNNNE (1206, X7R, 5 cents) and the inductor
is ANR6045T470M (6mm x 6mm, 0.25 ohm ESR, also 5 cents). I'm splurging
on the polyswitch (RXEF030, about 12 cents). That's seven parts on each
polarity, amortized over all the rails, not counting the RF bypass cap
and TVS (SMBJ15A, about 8 cents).
The regulators typically have 50 dB-ish rejection near DC, some
considerably less, but then go into the tank above 1 kHz or so, like
20-25 dB at 10 kHz. (Lasse's one is about 20 dB better there, for an
extra buck per rail). Discrete front ends have no PSR to speak of, so I
really need > 60 dB from hum frequencies to 10 kHz, and much better
above there.
So it's looking like a cap multiplier supervised by an LM4041 shunt
reference as the next stage. That's about a dozen parts per rail, which
isn't brilliant. It's hard to share them, because two of the rails need
to be near the negative input supply.
Humph.
Maybe make a regulator with an opamp and a mosfet or bipolar follower?
I'm lucky, I guess, that I don't have to sweat over pennies. Our
selling price over parts cost ratio is pretty high. I'd hate to be
making stuff where a gang of competitors are battling over price.
On 2026-02-19 14:16, john larkin wrote:
On Thu, 19 Feb 2026 13:50:52 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2026-02-18 22:34, john larkin wrote:
On Wed, 18 Feb 2026 22:12:12 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
Is generally the pits.
Anybody got a fave negative regulator with decent PSR?-a I need a
few rails
at no more than 150 mA, and the landscape is bleak.
The 337-style ones seem to rule the roost, and they stink.
IrCOm thinking of using TCA0372s, but they donrCOt have a PSR spec at all.
Cheers
Phil Hobbs
TPS723xx claims ultra low noise and high PSRR.
I like to put an RC at the input of a lin reg. That improves hf psrr,
shares some power dissipation, and gives me a way to measure the
current.
I like to bypass the top resistor in a feedback divider too.
About 20 dB at 10 kHz. :(-a They're almost all like that.
I guess that the substrate is the unreg input on a negative regulator,
so it couples into everything.
I've got a four-pole RLC LPF on each input that's -3 dB at 12 kHz and
(theoretically) -100 dB at 300 kHz, before veering off into spherical
meadows of -150 to -220 dB from 1-a to 50 MHz. ;)-a-a Simulation shows no >>> peaking and no overshoot.
-a-a-a-a-a-a 1 ohm-a-a-a-a-a-a-a 2 ohm-a-a-a 47u
Supply 0---POLYSWITCH--*--RRRR--*--LLLLLL---*--0-a --> vregs
-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a |-a-a-a-a-a-a-a |-a-a-a-a-a-a-a-a-a-a |
-a-a-a-a-a-a-a 4.7 uF (about-a CCC-a-a-a-a-a CCC 4.7uF-a-a CCC
-a-a-a-a-a-a-a 3.3 @ 15V)-a-a-a-a CCC-a-a-a-a-a CCC-a-a-a-a-a-a-a-a CCC 2x 4.7uF
-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a |-a-a-a-a-a-a-a |-a-a-a-a-a-a-a-a-a-a |
-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a GND-a-a-a-a-a GND-a-a-a-a-a-a-a-a GND
Maybe get some 150 uF polymer caps?
The caps are all CL31B475KAHNNNE (1206, X7R, 5 cents) and the inductor
is ANR6045T470M (6mm x 6mm, 0.25 ohm ESR, also 5 cents). I'm splurging
on the polyswitch (RXEF030, about 12 cents).-a That's seven parts on each >>> polarity, amortized over all the rails, not counting the RF bypass cap
and TVS (SMBJ15A, about 8 cents).
The regulators typically have 50 dB-ish rejection near DC, some
considerably less, but then go into the tank above 1 kHz or so, like
20-25 dB at 10 kHz.-a (Lasse's one is about 20 dB better there, for an
extra buck per rail).-a Discrete front ends have no PSR to speak of, so I >>> really need > 60 dB from hum frequencies to 10 kHz, and much better
above there.
So it's looking like a cap multiplier supervised by an LM4041 shunt
reference as the next stage.-a That's about a dozen parts per rail, which >>> isn't brilliant.-a It's hard to share them, because two of the rails need >>> to be near the negative input supply.
Humph.
Maybe make a regulator with an opamp and a mosfet or bipolar follower?
I'm lucky, I guess, that I don't have to sweat over pennies. Our
selling price over parts cost ratio is pretty high. I'd hate to be
making stuff where a gang of competitors are battling over price.
I think that's right.-a N-type Si substrates certainly exist, but IIRC
they aren't common except for some photodiodes.-a One might wish that the old saying "reverse polarity and use PNPs" were more applicable to
low-cost bipolar processes. ;)
Re: Regulator
After doing something fancier, and then Muntzing it down, I managed to
make a reasonable regulator (60ish dB near DC, 70ish from a few
kilohertz up) with only 10 cheap parts.-a No current limit, but oh
well--the quiet supply doesn't have to run any external outputs.-a It piggybacks a bit from a -5V rail generated by an LM337L, which saves a
zener diode for biasing the cascode transistor on the LM4041-Adj.
I had to fudge the modeal a bit, because none of the LM4041-Adj models I
can find actually work in LTspice. (Dunno about pspice.)-a Even the
TLV431 models don't seem to work in AC mode--they don't sink any current
for some reason.
The LM4041 and LM385 adjustable refs look like a PNP
transistor--feedback makes the reference voltage appear between ADJ and cathode, so if you want 1.2V, you connect ADJ to anode.-a That's super useful for negative supplies, because you can ground the anode and
connect the feedback divider between output and ground.
The more common TLV431 and its ilk are NPN-style, where the reference voltage appears between ADJ and anode, and connecting ADJ to cathode
makes a 1.2V reference.
To make the NPN-style work like a PNP, there's a voltage-controlled
voltage (e) source to effectively move the reference terminals.
Hopefully the AC characteristics of the two chips are similar
enough--the mid- and high-frequency behavior is mostly determined by the
BJT and passives anyway.
Here's the current iteration, including a screen shot.-a Unfortunately
the LM4041 model doesn't seem to work in .ac mode, so it's several .tran simulations instead.
<https://electrooptical.net/www/sed/NegRegCapMultSED.zip>
On 2026-02-19 21:57, Phil Hobbs wrote:
On 2026-02-19 14:16, john larkin wrote:
On Thu, 19 Feb 2026 13:50:52 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2026-02-18 22:34, john larkin wrote:
On Wed, 18 Feb 2026 22:12:12 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
Is generally the pits.
Anybody got a fave negative regulator with decent PSR?a I need a
few rails
at no more than 150 mA, and the landscape is bleak.
The 337-style ones seem to rule the roost, and they stink.
IAm thinking of using TCA0372s, but they donAt have a PSR spec at all. >>>>>>
Cheers
Phil Hobbs
TPS723xx claims ultra low noise and high PSRR.
I like to put an RC at the input of a lin reg. That improves hf psrr, >>>>> shares some power dissipation, and gives me a way to measure the
current.
I like to bypass the top resistor in a feedback divider too.
About 20 dB at 10 kHz. :(a They're almost all like that.
I guess that the substrate is the unreg input on a negative regulator,
so it couples into everything.
I've got a four-pole RLC LPF on each input that's -3 dB at 12 kHz and
(theoretically) -100 dB at 300 kHz, before veering off into spherical
meadows of -150 to -220 dB from 1a to 50 MHz. ;)aa Simulation shows no >>>> peaking and no overshoot.
aaaaaa 1 ohmaaaaaaa 2 ohmaaa 47u
Supply 0---POLYSWITCH--*--RRRR--*--LLLLLL---*--0a --> vregs
aaaaaaaaaaaaaaaaaaaaaaa |aaaaaaa |aaaaaaaaaa |
aaaaaaa 4.7 uF (abouta CCCaaaaa CCC 4.7uFaa CCC
aaaaaaa 3.3 @ 15V)aaaa CCCaaaaa CCCaaaaaaaa CCC 2x 4.7uF
aaaaaaaaaaaaaaaaaaaaaaa |aaaaaaa |aaaaaaaaaa |
aaaaaaaaaaaaaaaaaaaaaa GNDaaaaa GNDaaaaaaaa GND
Maybe get some 150 uF polymer caps?
The caps are all CL31B475KAHNNNE (1206, X7R, 5 cents) and the inductor >>>> is ANR6045T470M (6mm x 6mm, 0.25 ohm ESR, also 5 cents). I'm splurging >>>> on the polyswitch (RXEF030, about 12 cents).a That's seven parts on each >>>> polarity, amortized over all the rails, not counting the RF bypass cap >>>> and TVS (SMBJ15A, about 8 cents).
The regulators typically have 50 dB-ish rejection near DC, some
considerably less, but then go into the tank above 1 kHz or so, like
20-25 dB at 10 kHz.a (Lasse's one is about 20 dB better there, for an
extra buck per rail).a Discrete front ends have no PSR to speak of, so I >>>> really need > 60 dB from hum frequencies to 10 kHz, and much better
above there.
So it's looking like a cap multiplier supervised by an LM4041 shunt
reference as the next stage.a That's about a dozen parts per rail, which >>>> isn't brilliant.a It's hard to share them, because two of the rails need >>>> to be near the negative input supply.
Humph.
Maybe make a regulator with an opamp and a mosfet or bipolar follower?
I'm lucky, I guess, that I don't have to sweat over pennies. Our
selling price over parts cost ratio is pretty high. I'd hate to be
making stuff where a gang of competitors are battling over price.
I think that's right.a N-type Si substrates certainly exist, but IIRC
they aren't common except for some photodiodes.a One might wish that the
old saying "reverse polarity and use PNPs" were more applicable to
low-cost bipolar processes. ;)
Re: Regulator
After doing something fancier, and then Muntzing it down, I managed to
make a reasonable regulator (60ish dB near DC, 70ish from a few
kilohertz up) with only 10 cheap parts.a No current limit, but oh
well--the quiet supply doesn't have to run any external outputs.a It
piggybacks a bit from a -5V rail generated by an LM337L, which saves a
zener diode for biasing the cascode transistor on the LM4041-Adj.
I had to fudge the modeal a bit, because none of the LM4041-Adj models I
can find actually work in LTspice. (Dunno about pspice.)a Even the
TLV431 models don't seem to work in AC mode--they don't sink any current
for some reason.
The LM4041 and LM385 adjustable refs look like a PNP
transistor--feedback makes the reference voltage appear between ADJ and
cathode, so if you want 1.2V, you connect ADJ to anode.a That's super
useful for negative supplies, because you can ground the anode and
connect the feedback divider between output and ground.
The more common TLV431 and its ilk are NPN-style, where the reference
voltage appears between ADJ and anode, and connecting ADJ to cathode
makes a 1.2V reference.
To make the NPN-style work like a PNP, there's a voltage-controlled
voltage (e) source to effectively move the reference terminals.
Hopefully the AC characteristics of the two chips are similar
enough--the mid- and high-frequency behavior is mostly determined by the
BJT and passives anyway.
Here's the current iteration, including a screen shot.a Unfortunately
the LM4041 model doesn't seem to work in .ac mode, so it's several .tran
simulations instead.
<https://electrooptical.net/www/sed/NegRegCapMultSED.zip>
I just did some positive PSR measurements on a TCA0372. Conditions were
a single +10V supply with 200 mV p-p sinusoidal ripple, courtesy of my >trusty Siglent arb. I had to use one of our LA-22 100x precision low
noise lab amps to be able to see the feedthrough on a scope. (I could
also have broken out the lock-in, of course.)
Amp is wired as a follower, with a 3.3V lithium battery providing its
input. PSR is calculated as
PSR = 20*log(p-p ripple/200 mV)
Verdict: Awesome.
Freq Ripple PSR
1 kHz 3 uV 96 dB
10 kHz 5 uV 92 dB
20 kHz 14 uV 83 dB
50 kHz 12 uV 84 dB
100 kHz 40 uV 74 dB
200 kHz 500 uV 52 dB
This is a lot better than an LM317.
My 25-cent RLC filter is 100 dB down at 300 kHz, so I should be laughing
as far as the positive rails are concerned.
Cheers
Phil Hobbs
e`On Fri, 20 Feb 2026 16:05:26 -0500, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2026-02-19 21:57, Phil Hobbs wrote:
On 2026-02-19 14:16, john larkin wrote:
On Thu, 19 Feb 2026 13:50:52 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2026-02-18 22:34, john larkin wrote:
On Wed, 18 Feb 2026 22:12:12 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
Is generally the pits.
Anybody got a fave negative regulator with decent PSR?-a I need a >>>>>>> few rails
at no more than 150 mA, and the landscape is bleak.
The 337-style ones seem to rule the roost, and they stink.
IrCOm thinking of using TCA0372s, but they donrCOt have a PSR spec at all.
Cheers
Phil Hobbs
TPS723xx claims ultra low noise and high PSRR.
I like to put an RC at the input of a lin reg. That improves hf psrr, >>>>>> shares some power dissipation, and gives me a way to measure the
current.
I like to bypass the top resistor in a feedback divider too.
About 20 dB at 10 kHz. :(-a They're almost all like that.
I guess that the substrate is the unreg input on a negative regulator, >>>> so it couples into everything.
I've got a four-pole RLC LPF on each input that's -3 dB at 12 kHz and >>>>> (theoretically) -100 dB at 300 kHz, before veering off into spherical >>>>> meadows of -150 to -220 dB from 1-a to 50 MHz. ;)-a-a Simulation shows no >>>>> peaking and no overshoot.
-a-a-a-a-a-a 1 ohm-a-a-a-a-a-a-a 2 ohm-a-a-a 47u
Supply 0---POLYSWITCH--*--RRRR--*--LLLLLL---*--0-a --> vregs
-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a |-a-a-a-a-a-a-a |-a-a-a-a-a-a-a-a-a-a |
-a-a-a-a-a-a-a 4.7 uF (about-a CCC-a-a-a-a-a CCC 4.7uF-a-a CCC
-a-a-a-a-a-a-a 3.3 @ 15V)-a-a-a-a CCC-a-a-a-a-a CCC-a-a-a-a-a-a-a-a CCC 2x 4.7uF
-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a |-a-a-a-a-a-a-a |-a-a-a-a-a-a-a-a-a-a |
-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a GND-a-a-a-a-a GND-a-a-a-a-a-a-a-a GND
Maybe get some 150 uF polymer caps?
The caps are all CL31B475KAHNNNE (1206, X7R, 5 cents) and the inductor >>>>> is ANR6045T470M (6mm x 6mm, 0.25 ohm ESR, also 5 cents). I'm splurging >>>>> on the polyswitch (RXEF030, about 12 cents).-a That's seven parts on each >>>>> polarity, amortized over all the rails, not counting the RF bypass cap >>>>> and TVS (SMBJ15A, about 8 cents).
The regulators typically have 50 dB-ish rejection near DC, some
considerably less, but then go into the tank above 1 kHz or so, like >>>>> 20-25 dB at 10 kHz.-a (Lasse's one is about 20 dB better there, for an >>>>> extra buck per rail).-a Discrete front ends have no PSR to speak of, so I >>>>> really need > 60 dB from hum frequencies to 10 kHz, and much better
above there.
So it's looking like a cap multiplier supervised by an LM4041 shunt
reference as the next stage.-a That's about a dozen parts per rail, which >>>>> isn't brilliant.-a It's hard to share them, because two of the rails need >>>>> to be near the negative input supply.
Humph.
Maybe make a regulator with an opamp and a mosfet or bipolar follower? >>>>
I'm lucky, I guess, that I don't have to sweat over pennies. Our
selling price over parts cost ratio is pretty high. I'd hate to be
making stuff where a gang of competitors are battling over price.
I think that's right.-a N-type Si substrates certainly exist, but IIRC
they aren't common except for some photodiodes.-a One might wish that the >>> old saying "reverse polarity and use PNPs" were more applicable to
low-cost bipolar processes. ;)
Re: Regulator
After doing something fancier, and then Muntzing it down, I managed to
make a reasonable regulator (60ish dB near DC, 70ish from a few
kilohertz up) with only 10 cheap parts.-a No current limit, but oh
well--the quiet supply doesn't have to run any external outputs.-a It
piggybacks a bit from a -5V rail generated by an LM337L, which saves a
zener diode for biasing the cascode transistor on the LM4041-Adj.
I had to fudge the modeal a bit, because none of the LM4041-Adj models I >>> can find actually work in LTspice. (Dunno about pspice.)-a Even the
TLV431 models don't seem to work in AC mode--they don't sink any current >>> for some reason.
The LM4041 and LM385 adjustable refs look like a PNP
transistor--feedback makes the reference voltage appear between ADJ and
cathode, so if you want 1.2V, you connect ADJ to anode.-a That's super
useful for negative supplies, because you can ground the anode and
connect the feedback divider between output and ground.
The more common TLV431 and its ilk are NPN-style, where the reference
voltage appears between ADJ and anode, and connecting ADJ to cathode
makes a 1.2V reference.
To make the NPN-style work like a PNP, there's a voltage-controlled
voltage (e) source to effectively move the reference terminals.
Hopefully the AC characteristics of the two chips are similar
enough--the mid- and high-frequency behavior is mostly determined by the >>> BJT and passives anyway.
Here's the current iteration, including a screen shot.-a Unfortunately
the LM4041 model doesn't seem to work in .ac mode, so it's several .tran >>> simulations instead.
<https://electrooptical.net/www/sed/NegRegCapMultSED.zip>
I just did some positive PSR measurements on a TCA0372. Conditions were
a single +10V supply with 200 mV p-p sinusoidal ripple, courtesy of my
trusty Siglent arb. I had to use one of our LA-22 100x precision low
noise lab amps to be able to see the feedthrough on a scope. (I could
also have broken out the lock-in, of course.)
Amp is wired as a follower, with a 3.3V lithium battery providing its
input. PSR is calculated as
PSR = 20*log(p-p ripple/200 mV)
Verdict: Awesome.
Freq Ripple PSR
1 kHz 3 uV 96 dB
10 kHz 5 uV 92 dB
20 kHz 14 uV 83 dB
50 kHz 12 uV 84 dB
100 kHz 40 uV 74 dB
200 kHz 500 uV 52 dB
This is a lot better than an LM317.
My 25-cent RLC filter is 100 dB down at 300 kHz, so I should be laughing
as far as the positive rails are concerned.
Cheers
Phil Hobbs
Are you planning to use the TCA power opamp as the voltage regulator?
That makes sense, since I think you want two regs anyhow.
We did some testing on that amp. The current limiting mostly doesn't
work so you can blow it up. It can be made c-load stable.
On 2026-02-20 16:21, john larkin wrote:
e`On Fri, 20 Feb 2026 16:05:26 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2026-02-19 21:57, Phil Hobbs wrote:
On 2026-02-19 14:16, john larkin wrote:
On Thu, 19 Feb 2026 13:50:52 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2026-02-18 22:34, john larkin wrote:
On Wed, 18 Feb 2026 22:12:12 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
Is generally the pits.
Anybody got a fave negative regulator with decent PSR?a I need a >>>>>>>> few rails
at no more than 150 mA, and the landscape is bleak.
The 337-style ones seem to rule the roost, and they stink.
IAm thinking of using TCA0372s, but they donAt have a PSR spec at all. >>>>>>>>
Cheers
Phil Hobbs
TPS723xx claims ultra low noise and high PSRR.
I like to put an RC at the input of a lin reg. That improves hf psrr, >>>>>>> shares some power dissipation, and gives me a way to measure the >>>>>>> current.
I like to bypass the top resistor in a feedback divider too.
About 20 dB at 10 kHz. :(a They're almost all like that.
I guess that the substrate is the unreg input on a negative regulator, >>>>> so it couples into everything.
I've got a four-pole RLC LPF on each input that's -3 dB at 12 kHz and >>>>>> (theoretically) -100 dB at 300 kHz, before veering off into spherical >>>>>> meadows of -150 to -220 dB from 1a to 50 MHz. ;)aa Simulation shows no >>>>>> peaking and no overshoot.
aaaaaa 1 ohmaaaaaaa 2 ohmaaa 47u
Supply 0---POLYSWITCH--*--RRRR--*--LLLLLL---*--0a --> vregs
aaaaaaaaaaaaaaaaaaaaaaa |aaaaaaa |aaaaaaaaaa |
aaaaaaa 4.7 uF (abouta CCCaaaaa CCC 4.7uFaa CCC
aaaaaaa 3.3 @ 15V)aaaa CCCaaaaa CCCaaaaaaaa CCC 2x 4.7uF
aaaaaaaaaaaaaaaaaaaaaaa |aaaaaaa |aaaaaaaaaa |
aaaaaaaaaaaaaaaaaaaaaa GNDaaaaa GNDaaaaaaaa GND
Maybe get some 150 uF polymer caps?
The caps are all CL31B475KAHNNNE (1206, X7R, 5 cents) and the inductor >>>>>> is ANR6045T470M (6mm x 6mm, 0.25 ohm ESR, also 5 cents). I'm splurging >>>>>> on the polyswitch (RXEF030, about 12 cents).a That's seven parts on each >>>>>> polarity, amortized over all the rails, not counting the RF bypass cap >>>>>> and TVS (SMBJ15A, about 8 cents).
The regulators typically have 50 dB-ish rejection near DC, some
considerably less, but then go into the tank above 1 kHz or so, like >>>>>> 20-25 dB at 10 kHz.a (Lasse's one is about 20 dB better there, for an >>>>>> extra buck per rail).a Discrete front ends have no PSR to speak of, so I >>>>>> really need > 60 dB from hum frequencies to 10 kHz, and much better >>>>>> above there.
So it's looking like a cap multiplier supervised by an LM4041 shunt >>>>>> reference as the next stage.a That's about a dozen parts per rail, which >>>>>> isn't brilliant.a It's hard to share them, because two of the rails need >>>>>> to be near the negative input supply.
Humph.
Maybe make a regulator with an opamp and a mosfet or bipolar follower? >>>>>
I'm lucky, I guess, that I don't have to sweat over pennies. Our
selling price over parts cost ratio is pretty high. I'd hate to be
making stuff where a gang of competitors are battling over price.
I think that's right.a N-type Si substrates certainly exist, but IIRC
they aren't common except for some photodiodes.a One might wish that the >>>> old saying "reverse polarity and use PNPs" were more applicable to
low-cost bipolar processes. ;)
Re: Regulator
After doing something fancier, and then Muntzing it down, I managed to >>>> make a reasonable regulator (60ish dB near DC, 70ish from a few
kilohertz up) with only 10 cheap parts.a No current limit, but oh
well--the quiet supply doesn't have to run any external outputs.a It
piggybacks a bit from a -5V rail generated by an LM337L, which saves a >>>> zener diode for biasing the cascode transistor on the LM4041-Adj.
I had to fudge the modeal a bit, because none of the LM4041-Adj models I >>>> can find actually work in LTspice. (Dunno about pspice.)a Even the
TLV431 models don't seem to work in AC mode--they don't sink any current >>>> for some reason.
The LM4041 and LM385 adjustable refs look like a PNP
transistor--feedback makes the reference voltage appear between ADJ and >>>> cathode, so if you want 1.2V, you connect ADJ to anode.a That's super
useful for negative supplies, because you can ground the anode and
connect the feedback divider between output and ground.
The more common TLV431 and its ilk are NPN-style, where the reference
voltage appears between ADJ and anode, and connecting ADJ to cathode
makes a 1.2V reference.
To make the NPN-style work like a PNP, there's a voltage-controlled
voltage (e) source to effectively move the reference terminals.
Hopefully the AC characteristics of the two chips are similar
enough--the mid- and high-frequency behavior is mostly determined by the >>>> BJT and passives anyway.
Here's the current iteration, including a screen shot.a Unfortunately
the LM4041 model doesn't seem to work in .ac mode, so it's several .tran >>>> simulations instead.
<https://electrooptical.net/www/sed/NegRegCapMultSED.zip>
I just did some positive PSR measurements on a TCA0372. Conditions were >>> a single +10V supply with 200 mV p-p sinusoidal ripple, courtesy of my
trusty Siglent arb. I had to use one of our LA-22 100x precision low
noise lab amps to be able to see the feedthrough on a scope. (I could
also have broken out the lock-in, of course.)
Amp is wired as a follower, with a 3.3V lithium battery providing its
input. PSR is calculated as
PSR = 20*log(p-p ripple/200 mV)
Verdict: Awesome.
Freq Ripple PSR
1 kHz 3 uV 96 dB
10 kHz 5 uV 92 dB
20 kHz 14 uV 83 dB
50 kHz 12 uV 84 dB
100 kHz 40 uV 74 dB
200 kHz 500 uV 52 dB
This is a lot better than an LM317.
My 25-cent RLC filter is 100 dB down at 300 kHz, so I should be laughing >>> as far as the positive rails are concerned.
Cheers
Phil Hobbs
Are you planning to use the TCA power opamp as the voltage regulator?
That makes sense, since I think you want two regs anyhow.
We did some testing on that amp. The current limiting mostly doesn't
work so you can blow it up. It can be made c-load stable.
This guy is going to be loafing, so a 1-ohm series resistor and a cap
from the amp output to SJ should work well, I think. Barefoot, it
doesn't like capacitance one bit--the datasheet graph shows instability >starting at low-nanofarad loads even at a closed-loop gain of 100. (The >thing's A_VOL is only 3000 or so.)
I wish I only needed two rails. On account of the limitations of
available cheapish parts (which have virtues good enough to make this >worthwhile), I actually need ten, counting the reference.
VCC/VEE: +-13.5ish, to run the output amps. These don't need much PSR, >because of the RLC filters and the low-frequency PSR of the LM6171A
output amps. AP2205 for VCC, probably LM337M for VEE, with attention to
its dropout voltage.
VQ+ / VQ-: +-12ish, super quiet for the discrete front end (These have
to be strictly between VEE and VCC.) Both come from the TCA0372.
+5 analog: back-end muxes and op amps. AP2205.
+6.6V for the photodiode current monitors (ZXCT213), running on VQ and
+6.6 for sensing near VQ-. Super nice chip. I could use +5Q for this,
at some sacrifice of range and/or noise.
+3.3 reference for the ADS7054 ADC. I'm using a REF1933 for this, which >produces a half-scale reference for the full-diff amp as well.
+3.3 analog for the full-diff amp, ADCs, and sensors. This is a
filtered replica of the +3.3 reference. TCA0372.
+3.3 digital for MCU and so forth. AP2205.
-2.5 analog for a couple of op amps with 6V abs max. (I'll get the +2.5 >from +3.3 with a diode in series.) TCA0372.
Fun stuff.
Cheers
Phil Hobbs
On Fri, 20 Feb 2026 17:24:39 -0500, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2026-02-20 16:21, john larkin wrote:
e`On Fri, 20 Feb 2026 16:05:26 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2026-02-19 21:57, Phil Hobbs wrote:
On 2026-02-19 14:16, john larkin wrote:
On Thu, 19 Feb 2026 13:50:52 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2026-02-18 22:34, john larkin wrote:
On Wed, 18 Feb 2026 22:12:12 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
Is generally the pits.
Anybody got a fave negative regulator with decent PSR?-a I need a >>>>>>>>> few rails
at no more than 150 mA, and the landscape is bleak.
The 337-style ones seem to rule the roost, and they stink.
I-Am thinking of using TCA0372s, but they don-At have a PSR spec at all.
Cheers
Phil Hobbs
TPS723xx claims ultra low noise and high PSRR.
I like to put an RC at the input of a lin reg. That improves hf psrr, >>>>>>>> shares some power dissipation, and gives me a way to measure the >>>>>>>> current.
I like to bypass the top resistor in a feedback divider too.
About 20 dB at 10 kHz. :(-a They're almost all like that.
I guess that the substrate is the unreg input on a negative regulator, >>>>>> so it couples into everything.
I've got a four-pole RLC LPF on each input that's -3 dB at 12 kHz and >>>>>>> (theoretically) -100 dB at 300 kHz, before veering off into spherical >>>>>>> meadows of -150 to -220 dB from 1-a to 50 MHz. ;)-a-a Simulation shows no
peaking and no overshoot.
-a-a-a-a-a-a 1 ohm-a-a-a-a-a-a-a 2 ohm-a-a-a 47u
Supply 0---POLYSWITCH--*--RRRR--*--LLLLLL---*--0-a --> vregs
-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a |-a-a-a-a-a-a-a |-a-a-a-a-a-a-a-a-a-a |
-a-a-a-a-a-a-a 4.7 uF (about-a CCC-a-a-a-a-a CCC 4.7uF-a-a CCC
-a-a-a-a-a-a-a 3.3 @ 15V)-a-a-a-a CCC-a-a-a-a-a CCC-a-a-a-a-a-a-a-a CCC 2x 4.7uF
-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a |-a-a-a-a-a-a-a |-a-a-a-a-a-a-a-a-a-a |
-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a-a GND-a-a-a-a-a GND-a-a-a-a-a-a-a-a GND
Maybe get some 150 uF polymer caps?
The caps are all CL31B475KAHNNNE (1206, X7R, 5 cents) and the inductor >>>>>>> is ANR6045T470M (6mm x 6mm, 0.25 ohm ESR, also 5 cents). I'm splurging >>>>>>> on the polyswitch (RXEF030, about 12 cents).-a That's seven parts on each
polarity, amortized over all the rails, not counting the RF bypass cap >>>>>>> and TVS (SMBJ15A, about 8 cents).
The regulators typically have 50 dB-ish rejection near DC, some
considerably less, but then go into the tank above 1 kHz or so, like >>>>>>> 20-25 dB at 10 kHz.-a (Lasse's one is about 20 dB better there, for an >>>>>>> extra buck per rail).-a Discrete front ends have no PSR to speak of, so I
really need > 60 dB from hum frequencies to 10 kHz, and much better >>>>>>> above there.
So it's looking like a cap multiplier supervised by an LM4041 shunt >>>>>>> reference as the next stage.-a That's about a dozen parts per rail, which
isn't brilliant.-a It's hard to share them, because two of the rails need
to be near the negative input supply.
Humph.
Maybe make a regulator with an opamp and a mosfet or bipolar follower? >>>>>>
I'm lucky, I guess, that I don't have to sweat over pennies. Our
selling price over parts cost ratio is pretty high. I'd hate to be >>>>>> making stuff where a gang of competitors are battling over price.
I think that's right.-a N-type Si substrates certainly exist, but IIRC >>>>> they aren't common except for some photodiodes.-a One might wish that the >>>>> old saying "reverse polarity and use PNPs" were more applicable to
low-cost bipolar processes. ;)
Re: Regulator
After doing something fancier, and then Muntzing it down, I managed to >>>>> make a reasonable regulator (60ish dB near DC, 70ish from a few
kilohertz up) with only 10 cheap parts.-a No current limit, but oh
well--the quiet supply doesn't have to run any external outputs.-a It >>>>> piggybacks a bit from a -5V rail generated by an LM337L, which saves a >>>>> zener diode for biasing the cascode transistor on the LM4041-Adj.
I had to fudge the modeal a bit, because none of the LM4041-Adj models I >>>>> can find actually work in LTspice. (Dunno about pspice.)-a Even the
TLV431 models don't seem to work in AC mode--they don't sink any current >>>>> for some reason.
The LM4041 and LM385 adjustable refs look like a PNP
transistor--feedback makes the reference voltage appear between ADJ and >>>>> cathode, so if you want 1.2V, you connect ADJ to anode.-a That's super >>>>> useful for negative supplies, because you can ground the anode and
connect the feedback divider between output and ground.
The more common TLV431 and its ilk are NPN-style, where the reference >>>>> voltage appears between ADJ and anode, and connecting ADJ to cathode >>>>> makes a 1.2V reference.
To make the NPN-style work like a PNP, there's a voltage-controlled
voltage (e) source to effectively move the reference terminals.
Hopefully the AC characteristics of the two chips are similar
enough--the mid- and high-frequency behavior is mostly determined by the >>>>> BJT and passives anyway.
Here's the current iteration, including a screen shot.-a Unfortunately >>>>> the LM4041 model doesn't seem to work in .ac mode, so it's several .tran >>>>> simulations instead.
<https://electrooptical.net/www/sed/NegRegCapMultSED.zip>
I just did some positive PSR measurements on a TCA0372. Conditions were >>>> a single +10V supply with 200 mV p-p sinusoidal ripple, courtesy of my >>>> trusty Siglent arb. I had to use one of our LA-22 100x precision low
noise lab amps to be able to see the feedthrough on a scope. (I could >>>> also have broken out the lock-in, of course.)
Amp is wired as a follower, with a 3.3V lithium battery providing its
input. PSR is calculated as
PSR = 20*log(p-p ripple/200 mV)
Verdict: Awesome.
Freq Ripple PSR
1 kHz 3 uV 96 dB
10 kHz 5 uV 92 dB
20 kHz 14 uV 83 dB
50 kHz 12 uV 84 dB
100 kHz 40 uV 74 dB
200 kHz 500 uV 52 dB
This is a lot better than an LM317.
My 25-cent RLC filter is 100 dB down at 300 kHz, so I should be laughing >>>> as far as the positive rails are concerned.
Cheers
Phil Hobbs
Are you planning to use the TCA power opamp as the voltage regulator?
That makes sense, since I think you want two regs anyhow.
We did some testing on that amp. The current limiting mostly doesn't
work so you can blow it up. It can be made c-load stable.
This guy is going to be loafing, so a 1-ohm series resistor and a cap
from the amp output to SJ should work well, I think. Barefoot, it
doesn't like capacitance one bit--the datasheet graph shows instability
starting at low-nanofarad loads even at a closed-loop gain of 100. (The
thing's A_VOL is only 3000 or so.)
More capacitance can leapfrog the island of instability. A 56uF
polymer is good.
https://www.dropbox.com/scl/fi/1j1sgjh5tckznc811l5lx/TCA_and_56u.jpg?rlkey=6aqb876k0ez3jda2z6vdqmb8n&raw=1
https://www.dropbox.com/scl/fi/864x1fpj6xw8163m22njj/DSC00119.JPG?rlkey=sd64wh6qj76vyz1sj1t5v3kr6&raw=1
That's the Jim Williams idea: keep adding C until it stops
oscillating.
Incidentally, the TCA works fine at +5 volts supply.
I wish I only needed two rails. On account of the limitations of
available cheapish parts (which have virtues good enough to make this
worthwhile), I actually need ten, counting the reference.
VCC/VEE: +-13.5ish, to run the output amps. These don't need much PSR,
because of the RLC filters and the low-frequency PSR of the LM6171A
output amps. AP2205 for VCC, probably LM337M for VEE, with attention to
its dropout voltage.
VQ+ / VQ-: +-12ish, super quiet for the discrete front end (These have
to be strictly between VEE and VCC.) Both come from the TCA0372.
+5 analog: back-end muxes and op amps. AP2205.
+6.6V for the photodiode current monitors (ZXCT213), running on VQ and
+6.6 for sensing near VQ-. Super nice chip. I could use +5Q for this,
at some sacrifice of range and/or noise.
+3.3 reference for the ADS7054 ADC. I'm using a REF1933 for this, which
produces a half-scale reference for the full-diff amp as well.
+3.3 analog for the full-diff amp, ADCs, and sensors. This is a
filtered replica of the +3.3 reference. TCA0372.
+3.3 digital for MCU and so forth. AP2205.
-2.5 analog for a couple of op amps with 6V abs max. (I'll get the +2.5
from +3.3 with a diode in series.) TCA0372.
That's about 12 power supplies!
My new gadget, the PPG (Precision Pulse Generator) only needs about 7.
Interestingly, the most critical one, for noise and drift, is the 1.2
volt FPGA core supply. 100uV changes the prop delay more than I like.
That's about 12 power supplies!
My new gadget, the PPG (Precision Pulse Generator) only needs about 7.
Interestingly, the most critical one, for noise and drift, is the 1.2
volt FPGA core supply. 100uV changes the prop delay more than I like.
john larkin <jl@glen--canyon.com> wrote:
...
That's about 12 power supplies!Consider some stabilization loop. Some FPGA TDC design use similar >approaches.
My new gadget, the PPG (Precision Pulse Generator) only needs about 7.
Interestingly, the most critical one, for noise and drift, is the 1.2
volt FPGA core supply. 100uV changes the prop delay more than I like.
On 23 Feb 2026 22:57:00 GMT, Uwe Bonnes <bon@hertz.ikp.physik.tu-darmstadt.de> wrote:
john larkin <jl@glen--canyon.com> wrote:
...
That's about 12 power supplies!Consider some stabilization loop. Some FPGA TDC design use similar
My new gadget, the PPG (Precision Pulse Generator) only needs about 7.
Interestingly, the most critical one, for noise and drift, is the 1.2
volt FPGA core supply. 100uV changes the prop delay more than I like.
approaches.
I'm designing basically an economy DDG, digital delay generator. So
I'm not investing engineering hours or parts cost on extreme
performance.
So I'll just make the 1.2v supply as good as we reasonably can and
sell whatever it does.
Prop delay in the FPGA is about inverse on core power supply voltage.
If the supply is noisy, I don't think we could compensate for that in
real time.
We will know the PCB temperature so maybe we'll compensate for that a
little. That would be a quick test and a bit of code.
john larkin <jl@glen--canyon.com> wrote:
On 23 Feb 2026 22:57:00 GMT, Uwe Bonnes
<bon@hertz.ikp.physik.tu-darmstadt.de> wrote:
john larkin <jl@glen--canyon.com> wrote:
...
That's about 12 power supplies!Consider some stabilization loop. Some FPGA TDC design use similar
My new gadget, the PPG (Precision Pulse Generator) only needs about 7. >>>>
Interestingly, the most critical one, for noise and drift, is the 1.2
volt FPGA core supply. 100uV changes the prop delay more than I like.
approaches.
I'm designing basically an economy DDG, digital delay generator. So
I'm not investing engineering hours or parts cost on extreme
performance.
So I'll just make the 1.2v supply as good as we reasonably can and
sell whatever it does.
Prop delay in the FPGA is about inverse on core power supply voltage.
If the supply is noisy, I don't think we could compensate for that in
real time.
We will know the PCB temperature so maybe we'll compensate for that a
little. That would be a quick test and a bit of code.
Using a backwards PLL to regulate the supply would be pretty amusing,
though, you have to admit.
Cheers
Phil Hobbs
On Tue, 24 Feb 2026 00:46:22 -0000 (UTC), Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
john larkin <jl@glen--canyon.com> wrote:
On 23 Feb 2026 22:57:00 GMT, Uwe Bonnes
<bon@hertz.ikp.physik.tu-darmstadt.de> wrote:
john larkin <jl@glen--canyon.com> wrote:
...
That's about 12 power supplies!Consider some stabilization loop. Some FPGA TDC design use similar
My new gadget, the PPG (Precision Pulse Generator) only needs about 7. >>>>>
Interestingly, the most critical one, for noise and drift, is the 1.2 >>>>> volt FPGA core supply. 100uV changes the prop delay more than I like. >>>>>
approaches.
I'm designing basically an economy DDG, digital delay generator. So
I'm not investing engineering hours or parts cost on extreme
performance.
So I'll just make the 1.2v supply as good as we reasonably can and
sell whatever it does.
Prop delay in the FPGA is about inverse on core power supply voltage.
If the supply is noisy, I don't think we could compensate for that in
real time.
We will know the PCB temperature so maybe we'll compensate for that a
little. That would be a quick test and a bit of code.
Using a backwards PLL to regulate the supply would be pretty amusing,
though, you have to admit.
Cheers
Phil Hobbs
Yes. We couldn't compare the FPGA to an external delay line (they
aren't very good) so we'd need a clever (and affordable) way to
compare a prop delay to a clock.
Of course, every time you compile an FPGA design it may change the
routing radically.
Sometimes the optimizer decides that you really don't need to do
something at all.
But amusing is the enemy of cheap and done. That's a real problem in
this industry.
On Tue, 24 Feb 2026 00:46:22 -0000 (UTC), Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
john larkin <jl@glen--canyon.com> wrote:
On 23 Feb 2026 22:57:00 GMT, Uwe Bonnes
<bon@hertz.ikp.physik.tu-darmstadt.de> wrote:
john larkin <jl@glen--canyon.com> wrote:
...
That's about 12 power supplies!Consider some stabilization loop. Some FPGA TDC design use similar
My new gadget, the PPG (Precision Pulse Generator) only needs about 7. >>>>>
Interestingly, the most critical one, for noise and drift, is the 1.2 >>>>> volt FPGA core supply. 100uV changes the prop delay more than I like. >>>>>
approaches.
I'm designing basically an economy DDG, digital delay generator. So
I'm not investing engineering hours or parts cost on extreme
performance.
So I'll just make the 1.2v supply as good as we reasonably can and
sell whatever it does.
Prop delay in the FPGA is about inverse on core power supply voltage.
If the supply is noisy, I don't think we could compensate for that in
real time.
We will know the PCB temperature so maybe we'll compensate for that a
little. That would be a quick test and a bit of code.
Using a backwards PLL to regulate the supply would be pretty amusing,
though, you have to admit.
Cheers
Phil Hobbs
Yes. We couldn't compare the FPGA to an external delay line (they
aren't very good) so we'd need a clever (and affordable) way to
compare a prop delay to a clock.
Of course, every time you compile an FPGA design it may change the
routing radically.
Sometimes the optimizer decides that you really don't need to do
something at all.
But amusing is the enemy of cheap and done. That's a real problem in
this industry.
Yes. We couldn't compare the FPGA to an external delay line (they
aren't very good) so we'd need a clever (and affordable) way to
compare a prop delay to a clock.
Of course, every time you compile an FPGA design it may change the
routing radically.
Am 24.02.26 um 04:16 schrieb john larkin:
Yes. We couldn't compare the FPGA to an external delay line (they
aren't very good) so we'd need a clever (and affordable) way to
compare a prop delay to a clock.
I've built a switchable delay line from a reel of semi rigid coax,
heaps of SMA connectors and 3 pairs/stages of 1-to-6 coax relays.
The 1-to-6 relays were surprisingly cheap at ham radio meetings,
there exist not many apps for them.
The delay line could bring anything between 4 and 100 MHz into
phase quadrature for phase noise measurements.
It was a lot of work soldering SMAs, verifying / trimming cable
lengths on the TDR and packing everything into a 19" crate.
Exactly when I was done, I got hold of a Time Pod that could
do everything with 20 dB better pn resolution thanks to cross
correlation.
Of course, every time you compile an FPGA design it may change the
routing radically.
Back in Xilinx XC3020 times, a friend did his FPGA design
barefoot with the XACT editor by hand and he locked down every
connection and transmission gate. He ran out of luck when the next
chip delivery showed better but different timings.
He is a chip broker now.
Cheers, Gerhard
contemplating using the 337 on the basis of 317 PSRR specs. That would
be using the final output as the input to the ADJ on the pre-reg. You
should be able to get away with 3 Volt headroom, a bit more than the
stock 1.5V.
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