analog data link, with 6 to 12kV isolation

W

Winfield Hill

Guest
I need to make a simple analog data link, with 6 to 12kV
isolation capability. By simple, I mean 0.1% resolution
and 0.1% FS DC offset error, and maybe 20kHz bandwidth.
The goal is a scope-ready signal for our electrospinning
currents: 500nA FS, with less than 0.5nA noise and drift.

https://www.dropbox.com/sh/904n7auy3haeu3l/AAAlwbe5zCgHkJCwGrvHuEawa?dl=1

I'm thinking of using an ads1202 delta-sigma modulator,
and download its digital signal with an opi1268 coupler,
good to 16kV. See the datasheets in the dropbox folder.
We can run the modulator at 2MHz, the fastest speed the
coupler can handle. I'd like to use a simple low-pass
filter to convert the modulated signal to a DC voltage.
This means reconstituting the signal, while avoiding
problems from unequal rise and fall delays. But I have
a simple signal coding scheme in mind for doing that.


--
Thanks,
- Win
 
On 2019-11-03 21:40, Winfield Hill wrote:
I need to make a simple analog data link, with 6 to 12kV isolation
capability. By simple, I mean 0.1% resolution and 0.1% FS DC offset
error, and maybe 20kHz bandwidth. The goal is a scope-ready signal
for our electrospinning currents: 500nA FS, with less than 0.5nA
noise and drift.

https://www.dropbox.com/sh/904n7auy3haeu3l/AAAlwbe5zCgHkJCwGrvHuEawa?dl=1

I'm thinking of using an ads1202 delta-sigma modulator, and download
its digital signal with an opi1268 coupler, good to 16kV. See the
datasheets in the dropbox folder. We can run the modulator at 2MHz,
the fastest speed the coupler can handle. I'd like to use a simple
low-pass filter to convert the modulated signal to a DC voltage. This
means reconstituting the signal, while avoiding problems from unequal
rise and fall delays. But I have a simple signal coding scheme in
mind for doing that.
Click to expand...

Hello Winfield

2 MHz might be at the low end of the modulator's abilities. It's
supposed to handle down to 500 kHz at reduced accuracy, but the
recommended range is 16 - 24 MHz for an external clock.

Rather than being speed-limited by specialized 16 kV optocouplers,
consider pairs of TX/RX modules connected by a fiber. They can handle
data rates more appropriate for 20-ish MHz operation. Your application
does not seem to be very price-constrained, so a fiber pair may do it.

Connectorless receiver modules for plastic fibers like the IF-D97 or
IF-D91B from Industrial Fiber Optics might be useful, together with
matching transmitter modules. That way, the isolation is determined
entirely by the fiber, which can have an arbitrary length, allowing a
nice "any-kV" solution. It does not even have to be on one board.

To get rid of the risetime asymmetry, consider clocking the received
signal into a D-flipflop driven by the master modulator clock. The clock
can be generated on the LV side, used for the D-FF and sent to the HV
side by one fiber to be used as an external clock in "mode 3" of the
modulator. The data can travel back by a second fiber and be registered
by the LV-side D-FF. That would reduce the asymmetry to negligible
levels since D-FFs can be had with rather fast output risetimes.

Regards, Dimitrij
 
On 3 Nov 2019 12:40:16 -0800, Winfield Hill <winfieldhill@yahoo.com>
wrote:

I need to make a simple analog data link, with 6 to 12kV
isolation capability. By simple, I mean 0.1% resolution
and 0.1% FS DC offset error, and maybe 20kHz bandwidth.
The goal is a scope-ready signal for our electrospinning
currents: 500nA FS, with less than 0.5nA noise and drift.

https://www.dropbox.com/sh/904n7auy3haeu3l/AAAlwbe5zCgHkJCwGrvHuEawa?dl=1

I'm thinking of using an ads1202 delta-sigma modulator,
and download its digital signal with an opi1268 coupler,
good to 16kV. See the datasheets in the dropbox folder.
We can run the modulator at 2MHz, the fastest speed the
coupler can handle. I'd like to use a simple low-pass
filter to convert the modulated signal to a DC voltage.
This means reconstituting the signal, while avoiding
problems from unequal rise and fall delays. But I have
a simple signal coding scheme in mind for doing that.
Click to expand...

Always forcing two transistions per bit cell?

I'm using ADUM7703, isolating delta-sigma converter. But it's only
good for 8KV isolation.

Do you think you'll get low enough noise? With a 2 MHz clock, the
clock to bandwidth ratio is only 100:1.

You might clock it faster, and maybe use a fast fiber link for the
data, as Dimitrij suggests.

I have a 2nd order delta-sigma Spice model if that would help sim the
noise with your lowpass filter. I was planning to do the same thing,
analog filter the delta-sigma stream for some signal scope monitor
outputs, but then decided to have the FPGA drive serial DACs instead.



--

John Larkin Highland Technology, Inc

lunatic fringe electronics
 
On 2019-11-03 22:40, Dimitrij Klingbeil wrote:
On 2019-11-03 21:40, Winfield Hill wrote:
I need to make a simple analog data link, with 6 to 12kV isolation
capability. By simple, I mean 0.1% resolution and 0.1% FS DC
offset error, and maybe 20kHz bandwidth. The goal is a scope-ready
signal for our electrospinning currents: 500nA FS, with less than
0.5nA noise and drift.

https://www.dropbox.com/sh/904n7auy3haeu3l/AAAlwbe5zCgHkJCwGrvHuEawa?dl=1



I'm thinking of using an ads1202 delta-sigma modulator, and download
its digital signal with an opi1268 coupler, good to 16kV. See the
datasheets in the dropbox folder. We can run the modulator at
2MHz, the fastest speed the coupler can handle. I'd like to use a
simple low-pass filter to convert the modulated signal to a DC
voltage. This means reconstituting the signal, while avoiding
problems from unequal rise and fall delays. But I have a simple
signal coding scheme in mind for doing that.


Hello Winfield

2 MHz might be at the low end of the modulator's abilities. It's
supposed to handle down to 500 kHz at reduced accuracy, but the
recommended range is 16 - 24 MHz for an external clock.

Rather than being speed-limited by specialized 16 kV optocouplers,
consider pairs of TX/RX modules connected by a fiber. They can
handle data rates more appropriate for 20-ish MHz operation. Your
application does not seem to be very price-constrained, so a fiber
pair may do it.

Connectorless receiver modules for plastic fibers like the IF-D97 or
IF-D91B from Industrial Fiber Optics might be useful, together with
matching transmitter modules. That way, the isolation is determined
entirely by the fiber, which can have an arbitrary length, allowing
a nice "any-kV" solution. It does not even have to be on one board.

To get rid of the risetime asymmetry, consider clocking the received
signal into a D-flipflop driven by the master modulator clock. The
clock can be generated on the LV side, used for the D-FF and sent to
the HV side by one fiber to be used as an external clock in "mode 3"
of the modulator. The data can travel back by a second fiber and be
registered by the LV-side D-FF. That would reduce the asymmetry to
negligible levels since D-FFs can be had with rather fast output
risetimes.

Regards, Dimitrij
Click to expand...

P.S. While a pair of fiber modules does not need to be on one board, of
course it still can. Nothing prevents installing a TX/RX pair connected
by a short piece of plastic fiber all "inline" on the same board.
 
On Sunday, November 3, 2019 at 9:40:29 PM UTC+1, Winfield Hill wrote:
I need to make a simple analog data link, with 6 to 12kV
isolation capability. By simple, I mean 0.1% resolution
and 0.1% FS DC offset error, and maybe 20kHz bandwidth.
The goal is a scope-ready signal for our electrospinning
currents: 500nA FS, with less than 0.5nA noise and drift.

https://www.dropbox.com/sh/904n7auy3haeu3l/AAAlwbe5zCgHkJCwGrvHuEawa?dl=1

I'm thinking of using an ads1202 delta-sigma modulator,
and download its digital signal with an opi1268 coupler,
good to 16kV. See the datasheets in the dropbox folder.
We can run the modulator at 2MHz, the fastest speed the
coupler can handle. I'd like to use a simple low-pass
filter to convert the modulated signal to a DC voltage.
This means reconstituting the signal, while avoiding
problems from unequal rise and fall delays. But I have
a simple signal coding scheme in mind for doing that.


Being a cheapskate, always looking for minimum cost, I would sample the signal with an ADC (0.1% resolution would mean a 12bit ADC could do it)
Click to expand...

Then feed the serial data over spiral coils in the PCB (separated by prepeg for isolation)

Then into a 12 bit DAC

I would use 12 bit ADC and DAC from an microcontroller

You could do this at less than 1USD for the entire system, and then you would have 2 "free" microcontrollers

Cheers

Klaus
 
søndag den 3. november 2019 kl. 23.05.17 UTC+1 skrev jla...@highlandsniptechnology.com:
On 3 Nov 2019 12:40:16 -0800, Winfield Hill <winfieldhill@yahoo.com
wrote:

I need to make a simple analog data link, with 6 to 12kV
isolation capability. By simple, I mean 0.1% resolution
and 0.1% FS DC offset error, and maybe 20kHz bandwidth.
The goal is a scope-ready signal for our electrospinning
currents: 500nA FS, with less than 0.5nA noise and drift.

https://www.dropbox.com/sh/904n7auy3haeu3l/AAAlwbe5zCgHkJCwGrvHuEawa?dl=1

I'm thinking of using an ads1202 delta-sigma modulator,
and download its digital signal with an opi1268 coupler,
good to 16kV. See the datasheets in the dropbox folder.
We can run the modulator at 2MHz, the fastest speed the
coupler can handle. I'd like to use a simple low-pass
filter to convert the modulated signal to a DC voltage.
This means reconstituting the signal, while avoiding
problems from unequal rise and fall delays. But I have
a simple signal coding scheme in mind for doing that.

Always forcing two transistions per bit cell?

I'm using ADUM7703, isolating delta-sigma converter. But it's only
good for 8KV isolation.

Do you think you'll get low enough noise? With a 2 MHz clock, the
clock to bandwidth ratio is only 100:1.
Click to expand...

yeh, from the data sheet:

"Effective resolution of 12 bits can be maintained with
a digital filter bandwidth of 10kHz at a modulator rate of
10MHz"
 
On Sunday, 3 November 2019 21:45:44 UTC, Dimitrij Klingbeil wrote:
On 2019-11-03 22:40, Dimitrij Klingbeil wrote:
On 2019-11-03 21:40, Winfield Hill wrote:
I need to make a simple analog data link, with 6 to 12kV isolation
capability. By simple, I mean 0.1% resolution and 0.1% FS DC
offset error, and maybe 20kHz bandwidth. The goal is a scope-ready
signal for our electrospinning currents: 500nA FS, with less than
0.5nA noise and drift.

https://www.dropbox.com/sh/904n7auy3haeu3l/AAAlwbe5zCgHkJCwGrvHuEawa?dl=1



I'm thinking of using an ads1202 delta-sigma modulator, and download
its digital signal with an opi1268 coupler, good to 16kV. See the
datasheets in the dropbox folder. We can run the modulator at
2MHz, the fastest speed the coupler can handle. I'd like to use a
simple low-pass filter to convert the modulated signal to a DC
voltage. This means reconstituting the signal, while avoiding
problems from unequal rise and fall delays. But I have a simple
signal coding scheme in mind for doing that.


Hello Winfield

2 MHz might be at the low end of the modulator's abilities. It's
supposed to handle down to 500 kHz at reduced accuracy, but the
recommended range is 16 - 24 MHz for an external clock.

Rather than being speed-limited by specialized 16 kV optocouplers,
consider pairs of TX/RX modules connected by a fiber. They can
handle data rates more appropriate for 20-ish MHz operation. Your
application does not seem to be very price-constrained, so a fiber
pair may do it.

Connectorless receiver modules for plastic fibers like the IF-D97 or
IF-D91B from Industrial Fiber Optics might be useful, together with
matching transmitter modules. That way, the isolation is determined
entirely by the fiber, which can have an arbitrary length, allowing
a nice "any-kV" solution. It does not even have to be on one board.

To get rid of the risetime asymmetry, consider clocking the received
signal into a D-flipflop driven by the master modulator clock. The
clock can be generated on the LV side, used for the D-FF and sent to
the HV side by one fiber to be used as an external clock in "mode 3"
of the modulator. The data can travel back by a second fiber and be
registered by the LV-side D-FF. That would reduce the asymmetry to
negligible levels since D-FFs can be had with rather fast output
risetimes.

Regards, Dimitrij

P.S. While a pair of fiber modules does not need to be on one board, of
course it still can. Nothing prevents installing a TX/RX pair connected
by a short piece of plastic fiber all "inline" on the same board.
Click to expand...

It is worth considering 1Gbit/s (or faster) SFP fibre ethernet modules.
They can be used at much lower frequencies - limited by the 10nF
coupling capacitors that are normally used on the copper interfaces.
Many datacentres have now upgraded to 10Gbit/s so there are lots of
1Gbit/s modules on eBay for around $1. Don't be put off by multi-gigabit
fibre-channel modules - they will work just fine for 1 Gbit ethernet and
also work at much lower speeds if you want them to.
The only downsides I can think of are size and power consumption.

There are various choices of wavelength and single/multi-mode. For
your purposes it really will not matter as long as the wavelengths
match at both ends. You should use single-mode fibre with single-mode
SFPs, although for short lengths even getting this wrong doesn't
seem to matter.
Many MV of isolation and lots of bidirectional bandwidth for negligible
cost is very attractive.

John
 
On Sunday, November 3, 2019 at 12:40:29 PM UTC-8, Winfield Hill wrote:
I need to make a simple analog data link, with 6 to 12kV
isolation capability. By simple, I mean 0.1% resolution
and 0.1% FS DC offset error, and maybe 20kHz bandwidth.
The goal is a scope-ready signal for our electrospinning
currents: 500nA FS, with less than 0.5nA noise and drift.
Click to expand...

Looks do-able, but the optical isolator is a perhaps unnecessary
bottleneck; laser-based optics is faster, and a SFP laser module
and fiber, with a highspeed CD4046-variant as a V-F converter
would be my first stab . With 2-to-20 MHz frequency range, the
20 kHz response after demodulating would be an easy target to hit.

I'm probably guilty of trying to fit the problem into the parts
that reside in my junk collection...
 
On Monday, November 4, 2019 at 7:40:29 AM UTC+11, Winfield Hill wrote:
I need to make a simple analog data link, with 6 to 12kV
isolation capability. By simple, I mean 0.1% resolution
and 0.1% FS DC offset error, and maybe 20kHz bandwidth.
The goal is a scope-ready signal for our electrospinning
currents: 500nA FS, with less than 0.5nA noise and drift.

https://www.dropbox.com/sh/904n7auy3haeu3l/AAAlwbe5zCgHkJCwGrvHuEawa?dl=1

I'm thinking of using an ads1202 delta-sigma modulator,
and download its digital signal with an opi1268 coupler,
good to 16kV. See the datasheets in the dropbox folder.
We can run the modulator at 2MHz, the fastest speed the
coupler can handle. I'd like to use a simple low-pass
filter to convert the modulated signal to a DC voltage.
This means reconstituting the signal, while avoiding
problems from unequal rise and fall delays. But I have
a simple signal coding scheme in mind for doing that.
Click to expand...

Transmission line transformers can run a lot faster, and you can wind one on a ferrite ring with 12kV rated coaxial cable.

That makes it a moderately bulky component, but they are fine until you get up to frequencies where the wavelength in the transmission line starts getting down to the length of the transmission line - as you pointed out when I complained about the upper frequency limit I'd found on one I'd wound with twisted pair on an RM8 core.

--
Bill Sloman, Sydney
 
On Sunday, November 3, 2019 at 3:40:29 PM UTC-5, Winfield Hill wrote:
I need to make a simple analog data link, with 6 to 12kV
isolation capability. By simple, I mean 0.1% resolution
and 0.1% FS DC offset error, and maybe 20kHz bandwidth.
The goal is a scope-ready signal for our electrospinning
currents: 500nA FS, with less than 0.5nA noise and drift.

https://www.dropbox.com/sh/904n7auy3haeu3l/AAAlwbe5zCgHkJCwGrvHuEawa?dl=1

I'm thinking of using an ads1202 delta-sigma modulator,
and download its digital signal with an opi1268 coupler,
good to 16kV. See the datasheets in the dropbox folder.
We can run the modulator at 2MHz, the fastest speed the
coupler can handle. I'd like to use a simple low-pass
filter to convert the modulated signal to a DC voltage.
This means reconstituting the signal, while avoiding
problems from unequal rise and fall delays. But I have
a simple signal coding scheme in mind for doing that.
Click to expand...

To me this seems complex. Why bother with all these messy bits when a $4 CODEC can be used at each end? I guess you would need to either convey four signals across the opto interface or use a simple, small $4 FPGA to encode the samples into a single data stream. 16 bits * 48 ksps = 768 kbps. @96 ksps it's still only 1.5 Mbps. $8 at each end. Simple, small, inexpensive, reliable and repeatable. Heck, at 0.1% accuracy and linearity you could implement the CODEC in the FPGA as well.

--

Rick C.

- Get 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209
 
Dimitrij Klingbeil wrote...
On 2019-11-03 21:40, Winfield Hill wrote:
I need to make a simple analog data link, with 6 to 12kV isolation
capability. By simple, I mean 0.1% resolution and 0.1% FS DC offset
error, and maybe 20kHz bandwidth. The goal is a scope-ready signal
for our electrospinning currents: 500nA FS, with less than 0.5nA
noise and drift.

https://www.dropbox.com/sh/904n7auy3haeu3l/AAAlwbe5zCgHkJCwGrvHuEawa?dl=1

I'm thinking of using an ads1202 delta-sigma modulator, and download
its digital signal with an opi1268 coupler, good to 16kV. See the
datasheets in the dropbox folder. We can run the modulator at 2MHz,
the fastest speed the coupler can handle. I'd like to use a simple
low-pass filter to convert the modulated signal to a DC voltage. This
means reconstituting the signal, while avoiding problems from unequal
rise and fall delays. But I have a simple signal coding scheme in
mind for doing that.

Hello Winfield

2 MHz might be at the low end of the modulator's abilities. It's
supposed to handle down to 500 kHz at reduced accuracy, but the
recommended range is 16 - 24 MHz for an external clock.

Rather than being speed-limited by specialized 16 kV optocouplers,
consider pairs of TX/RX modules connected by a fiber. They can handle
data rates more appropriate for 20-ish MHz operation. Your application
does not seem to be very price-constrained, so a fiber pair may do it.

Connectorless receiver modules for plastic fibers like the IF-D97 or
IF-D91B from Industrial Fiber Optics might be useful, together with
matching transmitter modules. That way, the isolation is determined
entirely by the fiber, which can have an arbitrary length, allowing a
nice "any-kV" solution. It does not even have to be on one board.

To get rid of the risetime asymmetry, consider clocking the received
signal into a D-flipflop driven by the master modulator clock. The clock
can be generated on the LV side, used for the D-FF and sent to the HV
side by one fiber to be used as an external clock in "mode 3" of the
modulator. The data can travel back by a second fiber and be registered
by the LV-side D-FF. That would reduce the asymmetry to negligible
levels since D-FFs can be had with rather fast output risetimes.
Click to expand...

Thank you, Dimitrij. Yes, you laid out the things I've feared
and am hoping to avoid. But thanks anyway, for your specific
suggestions for a good choice of fiber optics. You are right
about the ads1202 not being suitable, besides the issue of its
performance at low speed, its MCLK is divided by 2 internally,
unfortunately killing my planned coding scheme, to combine a
good clock edge with the data, and use a single optocoupler.

However, if I instead use the older ads1201, with its 1MHz max
clock spec, and no divide-by-two, I should be able to resurrect
my single-wire coding scheme, which will have a D-flop re-sync
at the output. It'd be nice if I could run it at the coupler's
2MHz limit, but it'll probably be fast enough. And I can add
Industrial Fiber Optics modules on a PCB extension, an option
for use later on, in higher-voltage applications. For now I'm
hoping for low parts count and small occupied area of the PCB.


--
Thanks,
- Win
 
Rick C wrote...
On Sunday, November 3, 2019, Winfield Hill wrote:
I need to make a simple analog data link, with 6 to 12kV
isolation capability. By simple, I mean 0.1% resolution
and 0.1% FS DC offset error, and maybe 20kHz bandwidth.
The goal is a scope-ready signal for our electrospinning
currents: 500nA FS, with less than 0.5nA noise and drift.

I'm thinking of using an ads1202 delta-sigma modulator,
and download its digital signal with an opi1268 coupler,
good to 16kV. See the datasheets in the dropbox folder.
We can run the modulator at 2MHz, the fastest speed the
coupler can handle. I'd like to use a simple low-pass
filter to convert the modulated signal to a DC voltage.
This means reconstituting the signal, while avoiding
problems from unequal rise and fall delays. But I have
a simple signal coding scheme in mind for doing that.

To me this seems complex. Why bother with all these messy
bits when a $4 CODEC can be used at each end?
Click to expand...

You know of a 12kV CODEC for $4?

I guess you would need to either convey four signals across
the opto interface or use a simple, small $4 FPGA to encode
the samples into a single data stream.
Click to expand...

Yes, my plan is to encode MCLK and MDAT into one line.


--
Thanks,
- Win
 
On 5 Nov 2019 06:17:19 -0800, Winfield Hill <winfieldhill@yahoo.com>
wrote:

Dimitrij Klingbeil wrote...

On 2019-11-03 21:40, Winfield Hill wrote:
I need to make a simple analog data link, with 6 to 12kV isolation
capability. By simple, I mean 0.1% resolution and 0.1% FS DC offset
error, and maybe 20kHz bandwidth. The goal is a scope-ready signal
for our electrospinning currents: 500nA FS, with less than 0.5nA
noise and drift.

https://www.dropbox.com/sh/904n7auy3haeu3l/AAAlwbe5zCgHkJCwGrvHuEawa?dl=1

I'm thinking of using an ads1202 delta-sigma modulator, and download
its digital signal with an opi1268 coupler, good to 16kV. See the
datasheets in the dropbox folder. We can run the modulator at 2MHz,
the fastest speed the coupler can handle. I'd like to use a simple
low-pass filter to convert the modulated signal to a DC voltage. This
means reconstituting the signal, while avoiding problems from unequal
rise and fall delays. But I have a simple signal coding scheme in
mind for doing that.

Hello Winfield

2 MHz might be at the low end of the modulator's abilities. It's
supposed to handle down to 500 kHz at reduced accuracy, but the
recommended range is 16 - 24 MHz for an external clock.

Rather than being speed-limited by specialized 16 kV optocouplers,
consider pairs of TX/RX modules connected by a fiber. They can handle
data rates more appropriate for 20-ish MHz operation. Your application
does not seem to be very price-constrained, so a fiber pair may do it.

Connectorless receiver modules for plastic fibers like the IF-D97 or
IF-D91B from Industrial Fiber Optics might be useful, together with
matching transmitter modules. That way, the isolation is determined
entirely by the fiber, which can have an arbitrary length, allowing a
nice "any-kV" solution. It does not even have to be on one board.

To get rid of the risetime asymmetry, consider clocking the received
signal into a D-flipflop driven by the master modulator clock. The clock
can be generated on the LV side, used for the D-FF and sent to the HV
side by one fiber to be used as an external clock in "mode 3" of the
modulator. The data can travel back by a second fiber and be registered
by the LV-side D-FF. That would reduce the asymmetry to negligible
levels since D-FFs can be had with rather fast output risetimes.

Thank you, Dimitrij. Yes, you laid out the things I've feared
and am hoping to avoid. But thanks anyway, for your specific
suggestions for a good choice of fiber optics. You are right
about the ads1202 not being suitable, besides the issue of its
performance at low speed, its MCLK is divided by 2 internally,
unfortunately killing my planned coding scheme, to combine a
good clock edge with the data, and use a single optocoupler.

However, if I instead use the older ads1201, with its 1MHz max
clock spec, and no divide-by-two, I should be able to resurrect
my single-wire coding scheme, which will have a D-flop re-sync
at the output. It'd be nice if I could run it at the coupler's
2MHz limit, but it'll probably be fast enough. And I can add
Industrial Fiber Optics modules on a PCB extension, an option
for use later on, in higher-voltage applications. For now I'm
hoping for low parts count and small occupied area of the PCB.
Click to expand...

One of the d-s chips does Manchester, or you can make that with an xor
gate. Manchester has no DC component and is easy to recover on the
downstream side.



--

John Larkin Highland Technology, Inc

lunatic fringe electronics
 
On 5 Nov 2019 09:03:31 -0800, Winfield Hill <winfieldhill@yahoo.com>
wrote:

jlarkin@highlandsniptechnology.com wrote...

One of the d-s chips does Manchester, or you can make
that with an xor gate. Manchester has no DC component
and is easy to recover on the downstream side.

Yes I thought of that, and it's mode 2 with the ads1202.
But Manchester uses both polarities for its clock edge,
which with unequal coupler delays, means distorting the
duty cycle. I'm trying to avoid additional complexity,
like adding a PLL to eliminate clock jitter.

There's another way to get a single line: Use the middle
of my ads1201 external clock pulse to start an output
pulse, whose length will depend on whether MOUT is 1 or
0 at the time. This should give me a jitter-free
receiver clock, for free. :)
Click to expand...

OK, but that has a DC component so needs a DC-coupled link. And it
would care about duty-cycle distortion too.

I invented a simple Manchester decoder when I was mostly young and
stupid. I could probably remember that.



--

John Larkin Highland Technology, Inc

lunatic fringe electronics
 
jlarkin@highlandsniptechnology.com wrote...
One of the d-s chips does Manchester, or you can make
that with an xor gate. Manchester has no DC component
and is easy to recover on the downstream side.
Click to expand...

Yes I thought of that, and it's mode 2 with the ads1202.
But Manchester uses both polarities for its clock edge,
which with unequal coupler delays, means distorting the
duty cycle. I'm trying to avoid additional complexity,
like adding a PLL to eliminate clock jitter.

There's another way to get a single line: Use the middle
of my ads1201 external clock pulse to start an output
pulse, whose length will depend on whether MOUT is 1 or
0 at the time. This should give me a jitter-free
receiver clock, for free. :)


--
Thanks,
- Win
 
jlarkin@highlandsniptechnology.com wrote...
On 5 Nov 2019, Winfield Hill wrote:

There's another way to get a single line: Use the middle
of my ads1201 external clock pulse to start an output
pulse, whose length will depend on whether MOUT is 1 or
0 at the time. This should give me a jitter-free
receiver clock, for free. :)

OK, but that has a DC component so needs a DC-coupled link.
And it would care about duty-cycle distortion too.
Click to expand...

Most opto-couplers are DC links. I'll use the low-jitter
clock to reconstitute a good copy of the input signal, it
only takes a D-flop, like the mini-Gate you like to use.

I invented a simple Manchester decoder when I was
mostly young and stupid. I could probably remember that.
Click to expand...

It's a good way to send digital data, to use with a digital
filter, that be best, but I'm using an analog filter. :)

I'm not happy with the ads1201, and old part, 5V operation,
limited to 1MHz, in a big package, $20, etc. Newer parts,
like the amc1204, $6 in an soic-8 look better, but the spec
says 5MHz min. There's a 5Mbd OPI155, but it costs $66.


--
Thanks,
- Win
 
tirsdag den 5. november 2019 kl. 19.16.23 UTC+1 skrev Winfield Hill:
jlarkin@highlandsniptechnology.com wrote...

On 5 Nov 2019, Winfield Hill wrote:

There's another way to get a single line: Use the middle
of my ads1201 external clock pulse to start an output
pulse, whose length will depend on whether MOUT is 1 or
0 at the time. This should give me a jitter-free
receiver clock, for free. :)

OK, but that has a DC component so needs a DC-coupled link.
And it would care about duty-cycle distortion too.

Most opto-couplers are DC links. I'll use the low-jitter
clock to reconstitute a good copy of the input signal, it
only takes a D-flop, like the mini-Gate you like to use.

I invented a simple Manchester decoder when I was
mostly young and stupid. I could probably remember that.

It's a good way to send digital data, to use with a digital
filter, that be best, but I'm using an analog filter. :)

I'm not happy with the ads1201, and old part, 5V operation,
limited to 1MHz, in a big package, $20, etc. Newer parts,
like the amc1204, $6 in an soic-8 look better, but the spec
says 5MHz min. There's a 5Mbd OPI155, but it costs $66.
Click to expand...

how about a cheap mcu at each end? might be possible to use IrDa though it is suppposed to be max 115200kbaud for the simple 3/16 pulses
 
Lasse Langwadt Christensen wrote...
how about a cheap mcu at each end?
Click to expand...

If I do that, the ADC and DAC electronics is simple,
and one $6 2Mbd 15kV opto-coupler would be fine. I
just have to setup the controllers, and write code
for each end. It's tempting, but no longer simple.


--
Thanks,
- Win
 
On 5 Nov 2019 10:16:04 -0800, Winfield Hill <winfieldhill@yahoo.com>
wrote:

jlarkin@highlandsniptechnology.com wrote...

On 5 Nov 2019, Winfield Hill wrote:

There's another way to get a single line: Use the middle
of my ads1201 external clock pulse to start an output
pulse, whose length will depend on whether MOUT is 1 or
0 at the time. This should give me a jitter-free
receiver clock, for free. :)

OK, but that has a DC component so needs a DC-coupled link.
And it would care about duty-cycle distortion too.

Most opto-couplers are DC links. I'll use the low-jitter
clock to reconstitute a good copy of the input signal, it
only takes a D-flop, like the mini-Gate you like to use.

I invented a simple Manchester decoder when I was
mostly young and stupid. I could probably remember that.

It's a good way to send digital data, to use with a digital
filter, that be best, but I'm using an analog filter. :)
Click to expand...

The idea would be to reconstruct the absolute bit stream from the
Manchester and lowpass filter that. The signal into the analog filter
could come from a 1 ns Tiny flop, clocked at the rate that the d-s
chip uses.

Coupler timing distortion would be ignored, up to the point where
things break.

I'm not happy with the ads1201, and old part, 5V operation,
limited to 1MHz, in a big package, $20, etc. Newer parts,
like the amc1204, $6 in an soic-8 look better, but the spec
says 5MHz min. There's a 5Mbd OPI155, but it costs $66.
Click to expand...

My current design uses a bunch of ADUM7703s clocked at 20 MHz. It's an
SO8 with isolation, so I don't have a coupler problem.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
 
On Tuesday, November 5, 2019 at 2:34:23 PM UTC-5, Winfield Hill wrote:
Lasse Langwadt Christensen wrote...

how about a cheap mcu at each end?

If I do that, the ADC and DAC electronics is simple,
and one $6 2Mbd 15kV opto-coupler would be fine. I
just have to setup the controllers, and write code
for each end. It's tempting, but no longer simple.
Click to expand...

Strange... to me this *IS* simple. Worrying about jitter, DC coupling and duty cycle distortion sound messy and overly complicated to me.

--

Rick C.

-- Get 1,000 miles of free Supercharging
-- Tesla referral code - https://ts.la/richard11209
 
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