1.8 volts (max)

[Winfield Hill]

A middle-of-the-bee-hive insert, my little I2C
sensor module has five sensor ICs, comprising 12
sensor channels. All running on 3.3-volts, so I
thought. Then my programming associate, reading
the datasheets more carefully than I, pointed out
one of the gas sensors was limited to 1.8 volts.

What!? 1.8-volts absolute maximum!? Sheesh!
Back to the drawing board, add six more parts.


--
Thanks,
- Win

 

[John Larkin]

On 7 May 2019 18:49:19 -0700, Winfield Hill <hill@rowland.harvard.edu>
wrote:

A middle-of-the-bee-hive insert, my little I2C
sensor module has five sensor ICs, comprising 12
sensor channels. All running on 3.3-volts, so I
thought. Then my programming associate, reading
the datasheets more carefully than I, pointed out
one of the gas sensors was limited to 1.8 volts.

What!? 1.8-volts absolute maximum!? Sheesh!
Back to the drawing board, add six more parts.

Some FPGA and uP cores run at 1 volt, or even less.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Winfield Hill]

bitrex wrote...

On 5/7/19 9:49 PM, Winfield Hill wrote:
A middle-of-the-bee-hive insert, my little I2C
sensor module has five sensor ICs, comprising 12
sensor channels. All running on 3.3-volts, so I
thought. Then my programming associate, reading
the datasheets more carefully than I, pointed out
one of the gas sensors was limited to 1.8 volts.

What!? 1.8-volts absolute maximum!? Sheesh!
Back to the drawing board, add six more parts.

Two 1N4148?

The critical sensor in question, an SGP30 gas sensor,
is normally off, but draws 50mA running its heaters,
so needs a proper 1.8-volt regulator. Adafruit uses
an MIC5225, but that's too big, so I'm eyeing NCP170.
And an BSS138PS, for level shifting two I2C lines.


--
Thanks,
- Win

 

[bitrex]

On 5/7/19 9:49 PM, Winfield Hill wrote:

A middle-of-the-bee-hive insert, my little I2C
sensor module has five sensor ICs, comprising 12
sensor channels. All running on 3.3-volts, so I
thought. Then my programming associate, reading
the datasheets more carefully than I, pointed out
one of the gas sensors was limited to 1.8 volts.

What!? 1.8-volts absolute maximum!? Sheesh!
Back to the drawing board, add six more parts.

Two 1N4148?

 

[bitrex]

On 5/7/19 10:41 PM, John Larkin wrote:

On 7 May 2019 18:49:19 -0700, Winfield Hill <hill@rowland.harvard.edu
wrote:

A middle-of-the-bee-hive insert, my little I2C
sensor module has five sensor ICs, comprising 12
sensor channels. All running on 3.3-volts, so I
thought. Then my programming associate, reading
the datasheets more carefully than I, pointed out
one of the gas sensors was limited to 1.8 volts.

What!? 1.8-volts absolute maximum!? Sheesh!
Back to the drawing board, add six more parts.

Some FPGA and uP cores run at 1 volt, or even less.

A gentleman I know who works at Intel on portions of their most recent
designs would call 1 volt "high voltage"

 

[R Collins]

On Tuesday, May 7, 2019 at 10:36:36 PM UTC-4, Winfield Hill wrote:

bitrex wrote...

On 5/7/19 9:49 PM, Winfield Hill wrote:
A middle-of-the-bee-hive insert, my little I2C
sensor module has five sensor ICs, comprising 12
sensor channels. All running on 3.3-volts, so I
thought. Then my programming associate, reading
the datasheets more carefully than I, pointed out
one of the gas sensors was limited to 1.8 volts.

What!? 1.8-volts absolute maximum!? Sheesh!
Back to the drawing board, add six more parts.

Two 1N4148?

The critical sensor in question, an SGP30 gas sensor,
is normally off, but draws 50mA running its heaters,
so needs a proper 1.8-volt regulator. Adafruit uses
an MIC5225, but that's too big, so I'm eyeing NCP170.
And an BSS138PS, for level shifting two I2C lines.

I'm confused. Is the chip rated for 1.8 volts max, or 1.8 volts nominal?

For level shifting I like to use switch parts. I'm not sure if you can find parts that are intended to shift 3.3 down to 1.8, but the parts I used for interfacing 5.0 to 3.3 volts might work with the lower voltages. But I'm using 24 pin package parts, I expect you would want smaller devices.

--

Rick C.

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

 

[John Larkin]

On Tue, 7 May 2019 23:30:21 -0400, bitrex <user@example.net> wrote:

On 5/7/19 10:41 PM, John Larkin wrote:
On 7 May 2019 18:49:19 -0700, Winfield Hill <hill@rowland.harvard.edu
wrote:

A middle-of-the-bee-hive insert, my little I2C
sensor module has five sensor ICs, comprising 12
sensor channels. All running on 3.3-volts, so I
thought. Then my programming associate, reading
the datasheets more carefully than I, pointed out
one of the gas sensors was limited to 1.8 volts.

What!? 1.8-volts absolute maximum!? Sheesh!
Back to the drawing board, add six more parts.

Some FPGA and uP cores run at 1 volt, or even less.



A gentleman I know who works at Intel on portions of their most recent
designs would call 1 volt "high voltage"

0.5 volt, 200 amp switchers?


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

On Wednesday, 8 May 2019 03:36:36 UTC+1, Winfield Hill wrote:

bitrex wrote...
On 5/7/19 9:49 PM, Winfield Hill wrote:

A middle-of-the-bee-hive insert, my little I2C
sensor module has five sensor ICs, comprising 12
sensor channels. All running on 3.3-volts, so I
thought. Then my programming associate, reading
the datasheets more carefully than I, pointed out
one of the gas sensors was limited to 1.8 volts.

What!? 1.8-volts absolute maximum!? Sheesh!
Back to the drawing board, add six more parts.

Two 1N4148?

The critical sensor in question, an SGP30 gas sensor,
is normally off, but draws 50mA running its heaters,
so needs a proper 1.8-volt regulator. Adafruit uses
an MIC5225, but that's too big, so I'm eyeing NCP170.
And an BSS138PS, for level shifting two I2C lines.

This says it's 1.8 - 5v
https://www.adafruit.com/product/3709


NT

 

[Jasen Betts]

On 2019-05-08, tabbypurr@gmail.com <tabbypurr@gmail.com> wrote:

On Wednesday, 8 May 2019 03:36:36 UTC+1, Winfield Hill wrote:
bitrex wrote...
On 5/7/19 9:49 PM, Winfield Hill wrote:

A middle-of-the-bee-hive insert, my little I2C
sensor module has five sensor ICs, comprising 12
sensor channels. All running on 3.3-volts, so I
thought. Then my programming associate, reading
the datasheets more carefully than I, pointed out
one of the gas sensors was limited to 1.8 volts.

What!? 1.8-volts absolute maximum!? Sheesh!
Back to the drawing board, add six more parts.

Two 1N4148?

The critical sensor in question, an SGP30 gas sensor,
is normally off, but draws 50mA running its heaters,
so needs a proper 1.8-volt regulator. Adafruit uses
an MIC5225, but that's too big, so I'm eyeing NCP170.
And an BSS138PS, for level shifting two I2C lines.

This says it's 1.8 - 5v
https://www.adafruit.com/product/3709

yeah, but there's 7 extra parts on that board.

--
When I tried casting out nines I made a hash of it.

 

[Winfield Hill]

R Collins wrote...

Winfield Hill wrote:

The critical sensor in question, an SGP30 gas sensor,
is normally off, but draws 50mA running its heaters,
so needs a proper 1.8-volt regulator. Adafruit uses
an MIC5225, but that's too big, so I'm eyeing NCP170.
And an BSS138PS, for level shifting two I2C lines.

Now I'm eying the 150mA TPS71718 in SC-70-5.

I'm confused. Is the chip rated for 1.8 volts max,
or 1.8 volts nominal?

OK, right. It's 1.98 volts absolute maximum.

For level shifting I like to use switch parts. I'm
not sure if you can find parts that are intended to
shift 3.3 down to 1.8 ...

A simple MOSFET is the ultimate switch part.

.. 3.3V ,-----+--- 1.8V
.. | | |
.. 10k G 10k
.. 3.3V I2C logic --+-- D S --+-- 1.8V I2C logic
.. "S" "D"

The bidirectional I2C standard uses pulldown, with
pullup resistors to the local supply voltage. So a
simple MOSFET can handle the level shifting in both
directions. For low-to-high voltage, it's a cascode.
For high-to-low voltage, you can see the substrate
diode doing some work, but the drain of the MOSFET
becomes its "source", with the gate at 1.8 volts,
the "drain" pulls down with Rds(on) = 2 ohms for
BSS138. The '138PS is a dual version in SOT-363.


--
Thanks,
- Win

 

[R Collins]

On Wednesday, May 8, 2019 at 6:34:54 AM UTC-4, Winfield Hill wrote:

R Collins wrote...

Winfield Hill wrote:

The critical sensor in question, an SGP30 gas sensor,
is normally off, but draws 50mA running its heaters,
so needs a proper 1.8-volt regulator. Adafruit uses
an MIC5225, but that's too big, so I'm eyeing NCP170.
And an BSS138PS, for level shifting two I2C lines.

Now I'm eying the 150mA TPS71718 in SC-70-5.

I'm confused. Is the chip rated for 1.8 volts max,
or 1.8 volts nominal?

OK, right. It's 1.98 volts absolute maximum.

For level shifting I like to use switch parts. I'm
not sure if you can find parts that are intended to
shift 3.3 down to 1.8 ...

A simple MOSFET is the ultimate switch part.

. 3.3V ,-----+--- 1.8V
. | | |
. 10k G 10k
. 3.3V I2C logic --+-- D S --+-- 1.8V I2C logic
. "S" "D"

The bidirectional I2C standard uses pulldown, with
pullup resistors to the local supply voltage. So a
simple MOSFET can handle the level shifting in both
directions. For low-to-high voltage, it's a cascode.
For high-to-low voltage, you can see the substrate
diode doing some work, but the drain of the MOSFET
becomes its "source", with the gate at 1.8 volts,
the "drain" pulls down with Rds(on) = 2 ohms for
BSS138. The '138PS is a dual version in SOT-363.

Yes, that's what the switch parts are, pass FETs. But the gate needs a higher voltage than the low supply to turn on adequately over the voltage range. Otherwise you get weak passive pullups and slower performance.

The parts I use include a diode to shift the upper supply down enough to allow low resistance across the FET close to the lower V+ rail yeilding fast transitions by the drivers on either side. The drivers have to drive both load resistors in parallel so each should be twice the value. In your design once the 3 volt side releases the pull down and the voltage starts to rise, the FET will quickly become high resistance because of the 1.8 volt gate drive. So the low voltage side will only be pulled up by the single pullup which will be half as fast.

I haven't used I2C to know if this is an issue or not, but it should be considered. Likely you can use full strength pull ups on both sides and the drivers will drive them in parallel ok.

Oh, you might want to check the specs on your FET. The ON data sheet has a typical graph that shows the resistance rising *rapidly* below 2 volts Vgs.. That might not be the best part to use.

--

Rick C.

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

 

[bitrex]

On 5/7/19 11:45 PM, John Larkin wrote:

On Tue, 7 May 2019 23:30:21 -0400, bitrex <user@example.net> wrote:

On 5/7/19 10:41 PM, John Larkin wrote:
On 7 May 2019 18:49:19 -0700, Winfield Hill <hill@rowland.harvard.edu
wrote:

A middle-of-the-bee-hive insert, my little I2C
sensor module has five sensor ICs, comprising 12
sensor channels. All running on 3.3-volts, so I
thought. Then my programming associate, reading
the datasheets more carefully than I, pointed out
one of the gas sensors was limited to 1.8 volts.

What!? 1.8-volts absolute maximum!? Sheesh!
Back to the drawing board, add six more parts.

Some FPGA and uP cores run at 1 volt, or even less.



A gentleman I know who works at Intel on portions of their most recent
designs would call 1 volt "high voltage"

0.5 volt, 200 amp switchers?

The core voltage of the latest 5 and 3nm feature-size processors under
development is probably significantly below 0.5 volts but specifics
isn't information they give out to anybodies

 

[Winfield Hill]

R Collins wrote...

Yes, that's what the switch parts are, pass FETs.
But the gate needs a higher voltage than the low
supply to turn on adequately over the voltage range.
Otherwise you get weak passive pullups and slower
performance.

The parts I use include a diode to shift the upper
supply down enough to allow low resistance across
the FET close to the lower V+ rail yeilding fast
transitions by the drivers on either side. The
drivers have to drive both load resistors in
parallel so each should be twice the value.
In your design once the 3 volt side releases
the pull down and the voltage starts to rise,
the FET will quickly become high resistance
because of the 1.8 volt gate drive. So the
low voltage side will only be pulled up by
the single pullup which will be half as fast.

I haven't used I2C to know if this is an issue
or not, but it should be considered. Likely you
can use full strength pull ups on both sides
and the drivers will drive them in parallel ok.

It'd be interesting to learn what level-translator
chip you used. We have up to five feet of ugly
cable. Worried about possible pickup, we've
added 100pF caps on both lines, and will run
the bus slowly, 100kHz. So maybe we're OK.

Oh, you might want to check the specs on your
FET. The ON data sheet has a typical graph
that shows the resistance rising *rapidly*
below 2 volts Vgs. That might not be the
best part to use.

Yes, using a 60-volt part at 3.3 volts seems
silly, even if many others are using it. I
eyeballed NXP's curves to estimate the 2-ohm
number, but there must be a better part. I
do like the BSS138PS small SOT-363 package.


--
Thanks,
- Win

 

[Lasse Langwadt Christense]

onsdag den 8. maj 2019 kl. 18.49.25 UTC+2 skrev John Larkin:

On Wed, 8 May 2019 11:57:04 -0400, bitrex <user@example.net> wrote:

On 5/7/19 11:45 PM, John Larkin wrote:
On Tue, 7 May 2019 23:30:21 -0400, bitrex <user@example.net> wrote:

On 5/7/19 10:41 PM, John Larkin wrote:
On 7 May 2019 18:49:19 -0700, Winfield Hill <hill@rowland.harvard.edu
wrote:

A middle-of-the-bee-hive insert, my little I2C
sensor module has five sensor ICs, comprising 12
sensor channels. All running on 3.3-volts, so I
thought. Then my programming associate, reading
the datasheets more carefully than I, pointed out
one of the gas sensors was limited to 1.8 volts.

What!? 1.8-volts absolute maximum!? Sheesh!
Back to the drawing board, add six more parts.

Some FPGA and uP cores run at 1 volt, or even less.



A gentleman I know who works at Intel on portions of their most recent
designs would call 1 volt "high voltage"

0.5 volt, 200 amp switchers?



The core voltage of the latest 5 and 3nm feature-size processors under
development is probably significantly below 0.5 volts but specifics
isn't information they give out to anybodies

How can they distribute tens, or maybe hundreds, of amps on a chip?

very carefully I guess

https://www.intel.com/content/dam/www/public/us/en/documents/datasheets/8th-gen-core-family-datasheet-vol-1.pdf

40-193A Core Icc depending on number of cores..

no wonder some motherboards have voltage regulators with 8 or even more phases

 

[bitrex]

On 5/8/19 12:49 PM, John Larkin wrote:

On Wed, 8 May 2019 11:57:04 -0400, bitrex <user@example.net> wrote:

On 5/7/19 11:45 PM, John Larkin wrote:
On Tue, 7 May 2019 23:30:21 -0400, bitrex <user@example.net> wrote:

On 5/7/19 10:41 PM, John Larkin wrote:
On 7 May 2019 18:49:19 -0700, Winfield Hill <hill@rowland.harvard.edu
wrote:

A middle-of-the-bee-hive insert, my little I2C
sensor module has five sensor ICs, comprising 12
sensor channels. All running on 3.3-volts, so I
thought. Then my programming associate, reading
the datasheets more carefully than I, pointed out
one of the gas sensors was limited to 1.8 volts.

What!? 1.8-volts absolute maximum!? Sheesh!
Back to the drawing board, add six more parts.

Some FPGA and uP cores run at 1 volt, or even less.



A gentleman I know who works at Intel on portions of their most recent
designs would call 1 volt "high voltage"

0.5 volt, 200 amp switchers?



The core voltage of the latest 5 and 3nm feature-size processors under
development is probably significantly below 0.5 volts but specifics
isn't information they give out to anybodies

How can they distribute tens, or maybe hundreds, of amps on a chip?

Intel was using non-planar "3D" transistors in mass production as of the
22nm process, e.g. "FINFet."

<https://semiaccurate.com/2011/08/18/intel-moves-transistors-from-2d-to-3d-and-more/>

The 22nm process is pushing a decade ago, now, they're on to "Trigate"
and other topologies that again, my buddy cannot talk to me about and
possibly isn't even familiar with - he probably was barely old enough to
drive when that article was written! He does on-die cache memory
controller design/layout AFAIK that's all he does, Intel can afford to
super-specialize like that

 

[bitrex]

On 5/8/19 1:34 PM, Lasse Langwadt Christensen wrote:

onsdag den 8. maj 2019 kl. 18.49.25 UTC+2 skrev John Larkin:
On Wed, 8 May 2019 11:57:04 -0400, bitrex <user@example.net> wrote:

On 5/7/19 11:45 PM, John Larkin wrote:
On Tue, 7 May 2019 23:30:21 -0400, bitrex <user@example.net> wrote:

On 5/7/19 10:41 PM, John Larkin wrote:
On 7 May 2019 18:49:19 -0700, Winfield Hill <hill@rowland.harvard.edu
wrote:

A middle-of-the-bee-hive insert, my little I2C
sensor module has five sensor ICs, comprising 12
sensor channels. All running on 3.3-volts, so I
thought. Then my programming associate, reading
the datasheets more carefully than I, pointed out
one of the gas sensors was limited to 1.8 volts.

What!? 1.8-volts absolute maximum!? Sheesh!
Back to the drawing board, add six more parts.

Some FPGA and uP cores run at 1 volt, or even less.



A gentleman I know who works at Intel on portions of their most recent
designs would call 1 volt "high voltage"

0.5 volt, 200 amp switchers?



The core voltage of the latest 5 and 3nm feature-size processors under
development is probably significantly below 0.5 volts but specifics
isn't information they give out to anybodies

How can they distribute tens, or maybe hundreds, of amps on a chip?

very carefully I guess

https://www.intel.com/content/dam/www/public/us/en/documents/datasheets/8th-gen-core-family-datasheet-vol-1.pdf

40-193A Core Icc depending on number of cores..

no wonder some motherboards have voltage regulators with 8 or even more phases

Even my dumpy msi AMD Phenom II desktop mobo from 7 years ago has a
four-phase main regulator for the CPU with a pleasant set of blue LED
indicators to indicate activity

 

[John Larkin]

On Wed, 8 May 2019 11:57:04 -0400, bitrex <user@example.net> wrote:

On 5/7/19 11:45 PM, John Larkin wrote:
On Tue, 7 May 2019 23:30:21 -0400, bitrex <user@example.net> wrote:

On 5/7/19 10:41 PM, John Larkin wrote:
On 7 May 2019 18:49:19 -0700, Winfield Hill <hill@rowland.harvard.edu
wrote:

A middle-of-the-bee-hive insert, my little I2C
sensor module has five sensor ICs, comprising 12
sensor channels. All running on 3.3-volts, so I
thought. Then my programming associate, reading
the datasheets more carefully than I, pointed out
one of the gas sensors was limited to 1.8 volts.

What!? 1.8-volts absolute maximum!? Sheesh!
Back to the drawing board, add six more parts.

Some FPGA and uP cores run at 1 volt, or even less.



A gentleman I know who works at Intel on portions of their most recent
designs would call 1 volt "high voltage"

0.5 volt, 200 amp switchers?



The core voltage of the latest 5 and 3nm feature-size processors under
development is probably significantly below 0.5 volts but specifics
isn't information they give out to anybodies

How can they distribute tens, or maybe hundreds, of amps on a chip?


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[bitrex]

On 5/8/19 1:44 PM, bitrex wrote:

On 5/8/19 1:34 PM, Lasse Langwadt Christensen wrote:
onsdag den 8. maj 2019 kl. 18.49.25 UTC+2 skrev John Larkin:
On Wed, 8 May 2019 11:57:04 -0400, bitrex <user@example.net> wrote:

On 5/7/19 11:45 PM, John Larkin wrote:
On Tue, 7 May 2019 23:30:21 -0400, bitrex <user@example.net> wrote:

On 5/7/19 10:41 PM, John Larkin wrote:
On 7 May 2019 18:49:19 -0700, Winfield Hill
hill@rowland.harvard.edu
wrote:

A middle-of-the-bee-hive insert, my little I2C
sensor module has five sensor ICs, comprising 12
sensor channels.  All running on 3.3-volts, so I
thought.  Then my programming associate, reading
the datasheets more carefully than I, pointed out
one of the gas sensors was limited to 1.8 volts.

What!?  1.8-volts absolute maximum!?  Sheesh!
Back to the drawing board, add six more parts.

Some FPGA and uP cores run at 1 volt, or even less.



A gentleman I know who works at Intel on portions of their most
recent
designs would call 1 volt "high voltage"

0.5 volt, 200 amp switchers?



The core voltage of the latest 5 and 3nm feature-size processors under
development is probably significantly below 0.5 volts but specifics
isn't information they give out to anybodies

How can they distribute tens, or maybe hundreds, of amps on a chip?

very carefully I guess

https://www.intel.com/content/dam/www/public/us/en/documents/datasheets/8th-gen-core-family-datasheet-vol-1.pdf


40-193A Core Icc depending on number of cores..

no wonder some motherboards have voltage regulators with 8 or even
more phases



Even my dumpy msi AMD Phenom II desktop mobo from 7 years ago has a
four-phase main regulator for the CPU with a pleasant set of blue LED
indicators to indicate activity

they cheeped out on the design tho and uses a single power MOSFET as a
phase-splitter in the row of synchronous bucks instead of a proper
high-side driver, and it blows them repeatedly under high load :-(

 

[Winfield Hill]

John Larkin wrote...

The design and mask set costs for a bleeding-edge
chip is approaching a billion dollars.

And when I plunk down $600 for a 2066-pin X299
Intel CPU for my mobo, and know it's going to be
blisteringly fast, I'm making a contribution.


--
Thanks,
- Win

 

[John Larkin]

On Wed, 8 May 2019 13:39:19 -0400, bitrex <user@example.net> wrote:

On 5/8/19 12:49 PM, John Larkin wrote:
On Wed, 8 May 2019 11:57:04 -0400, bitrex <user@example.net> wrote:

On 5/7/19 11:45 PM, John Larkin wrote:
On Tue, 7 May 2019 23:30:21 -0400, bitrex <user@example.net> wrote:

On 5/7/19 10:41 PM, John Larkin wrote:
On 7 May 2019 18:49:19 -0700, Winfield Hill <hill@rowland.harvard.edu
wrote:

A middle-of-the-bee-hive insert, my little I2C
sensor module has five sensor ICs, comprising 12
sensor channels. All running on 3.3-volts, so I
thought. Then my programming associate, reading
the datasheets more carefully than I, pointed out
one of the gas sensors was limited to 1.8 volts.

What!? 1.8-volts absolute maximum!? Sheesh!
Back to the drawing board, add six more parts.

Some FPGA and uP cores run at 1 volt, or even less.



A gentleman I know who works at Intel on portions of their most recent
designs would call 1 volt "high voltage"

0.5 volt, 200 amp switchers?



The core voltage of the latest 5 and 3nm feature-size processors under
development is probably significantly below 0.5 volts but specifics
isn't information they give out to anybodies

How can they distribute tens, or maybe hundreds, of amps on a chip?



Intel was using non-planar "3D" transistors in mass production as of the
22nm process, e.g. "FINFet."

https://semiaccurate.com/2011/08/18/intel-moves-transistors-from-2d-to-3d-and-more/

The 22nm process is pushing a decade ago, now, they're on to "Trigate"
and other topologies that again, my buddy cannot talk to me about and
possibly isn't even familiar with - he probably was barely old enough to
drive when that article was written! He does on-die cache memory
controller design/layout AFAIK that's all he does, Intel can afford to
super-specialize like that

The design and mask set costs for a bleeding-edge chip is approaching
a billion dollars.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com