CV/CC synchronous buck -- do they exist?!...

[Piotr Wyderski]

Hi,

I need a simple synchronous buck converter capable of seamless CV/CC
transition. V_IN_MAX=17V, I_OUT=3-5A (roughly), V_OUT=3V. I had googled
a lot but was unable to find a nice part for the job. All the candidates
either have too low I_OUT, self-protect themselves like Jackie Chan with
various hiccup/latch off algorithms or require so many external
components that it is hard to distinguish them from a discrete solution
(the notorious LTC...). And the remaining few ones don\'t have legs,
which excludes them from the BOM.

Do you know of something as simple as TPS54302 which would just start
pumping current when overloaded? The limit value can be very rough; I
don\'t care. Or do I really need to roll my own old-school truly
hysteretic converter based on the INA293 or compatible and a bunch of
comparators?

Best regards, Piotr

 

[Phil Hobbs]

On 2020-07-16 03:55, Piotr Wyderski wrote:

Hi,

I need a simple synchronous buck converter capable of seamless CV/CC
transition. V_IN_MAX=17V, I_OUT=3-5A (roughly), V_OUT=3V. I had googled
a lot but was unable to find a nice part for the job. All the candidates
either have too low I_OUT, self-protect themselves like Jackie Chan with
various hiccup/latch off algorithms or require so many external
components that it is hard to distinguish them from a discrete solution
(the notorious LTC...). And the remaining few ones don\'t have legs,
which excludes them from the BOM.

Do you know of something as simple as TPS54302 which would just start
pumping current when overloaded? The limit value can be very rough; I
don\'t care. Or do I really need to roll my own old-school truly
hysteretic converter based on the INA293 or compatible and a bunch of
comparators?

    Best regards, Piotr

Switching regulator datasheets are the pits IME. Modern parts all seem
to have so much internal \'intelligence\' that they\'re about as
predictable as Eddie the shipboard computer in HHGTTG. The worst ones
lie through their teeth, such as the one for the MCP16312, which claims
that it keeps PWMing down to zero load, which it does not.

I never use a new switcher without prototyping it very carefully.

Cheers

Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Klaus Kragelund]

The old venerable UCC3825 and derivatives can be conrilled like you want. You do need to add high side driver though

Cheers

Klaus

 

[server]

On Thu, 16 Jul 2020 09:55:30 +0200, Piotr Wyderski
<peter.pan@neverland.mil> wrote:

Hi,

I need a simple synchronous buck converter capable of seamless CV/CC
transition. V_IN_MAX=17V, I_OUT=3-5A (roughly), V_OUT=3V. I had googled
a lot but was unable to find a nice part for the job. All the candidates
either have too low I_OUT, self-protect themselves like Jackie Chan with
various hiccup/latch off algorithms or require so many external
components that it is hard to distinguish them from a discrete solution
(the notorious LTC...). And the remaining few ones don\'t have legs,
which excludes them from the BOM.

Do you know of something as simple as TPS54302 which would just start
pumping current when overloaded? The limit value can be very rough; I
don\'t care. Or do I really need to roll my own old-school truly
hysteretic converter based on the INA293 or compatible and a bunch of
comparators?

Best regards, Piotr

My fave lately is LTM8078, which can be run in always-switch mode
(burpless) and does have an LT Spice model.

You can use half, or both halves in parallel for more current, or get
two separate voltages out, of either polarity.

But it is BGA. There is some standard LTC chip inside.

You could add a couple of parts to some dumb switcher, to add a
current component to the feedback.

Some of the old National Simple Switchers had cycle-by-cycle (peak)
current limiting. Nice, reliable, dumb parts. I just used an LM2576HV
to convert 48 volts to 12, at some absurdly low switching frequency.

https://www.dropbox.com/s/xywr3isogqnklm7/P901_E3.jpg?raw=1









--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[sea moss]

On Thursday, July 16, 2020 at 12:55:34 AM UTC-7, Piotr Wyderski wrote:

Hi,

I need a simple synchronous buck converter capable of seamless CV/CC
transition. V_IN_MAX=17V, I_OUT=3-5A (roughly), V_OUT=3V. I had googled
a lot but was unable to find a nice part for the job. All the candidates
either have too low I_OUT, self-protect themselves like Jackie Chan with
various hiccup/latch off algorithms or require so many external
components that it is hard to distinguish them from a discrete solution
(the notorious LTC...). And the remaining few ones don\'t have legs,
which excludes them from the BOM.

Do you know of something as simple as TPS54302 which would just start
pumping current when overloaded? The limit value can be very rough; I
don\'t care. Or do I really need to roll my own old-school truly
hysteretic converter based on the INA293 or compatible and a bunch of
comparators?

Best regards, Piotr

I think the Rohm BD9E30x series might work for you. I recently used the BD9E301 for my first-ever \"flybuck\", kind of fun. I\'m actually using an external current limit, since the 5A internal limit is too high for my magnetics (so I couldn\'t find the perfect part either. If you find a 1.5-2A equivalent let me know).

 

[Piotr Wyderski]

sea moss wrote:

> I think the Rohm BD9E30x series might work for you.

\"Short Circuit Protection (SCP) The short circuit protection block
compares the FB terminal voltage with the internal reference voltage
VREF. When the FB terminal voltage has fallen below 0.85V (Typ) and
remained in that state for 1.0msec (Typ), SCP activates andstops the
operation for 16msec (Typ) and subsequently initiates a restart.\"

TL;DR: no CC mode.

Best regards, Piotr

 

[Phil Hobbs]

On 2020-07-16 13:45, Piotr Wyderski wrote:

sea moss wrote:

I think the Rohm BD9E30x series might work for you.

\"Short Circuit Protection (SCP) The short circuit protection block
compares the FB terminal voltage with the internal reference voltage
VREF. When the FB terminal voltage has fallen below 0.85V   (Typ) and
remained in that state for 1.0msec (Typ), SCP activates andstops the
operation for 16msec (Typ) and subsequently initiates a restart.\"

TL;DR: no CC mode.

For my Class H TEC driver, I just dork the feedback pin with another
resistor to a DAC. You ought to be able to do the same thing with an op
amp to make a CC mode, if your switcher isn\'t too whizzy.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Piotr Wyderski]

sea moss wrote:

> I think the Rohm BD9E30x series might work for you.

\"Short Circuit Protection (SCP) The short circuit protection block
compares the FB terminal voltage with the internal reference voltage
VREF. When the FB terminal voltage has fallen below 0.85V (Typ) and
remained in that state for 1.0msec (Typ), SCP activates andstops the
operation for 16msec (Typ) and subsequently initiates a restart.\"

TL;DR: no CC mode.

Best regards, Piotr

 

[Piotr Wyderski]

sea moss wrote:

> I think the Rohm BD9E30x series might work for you.

\"Short Circuit Protection (SCP) The short circuit protection block
compares the FB terminal voltage with the internal reference voltage
VREF. When the FB terminal voltage has fallen below 0.85V (Typ) and
remained in that state for 1.0msec (Typ), SCP activates andstops the
operation for 16msec (Typ) and subsequently initiates a restart.\"

TL;DR: no CC mode.

Best regards, Piotr

 

[Mat Nieuwenhoven]

On Thu, 16 Jul 2020 09:55:30 +0200, Piotr Wyderski wrote:

Hi,

I need a simple synchronous buck converter capable of seamless CV/CC
transition. V_IN_MAX=17V, I_OUT=3-5A (roughly), V_OUT=3V. I had googled
a lot but was unable to find a nice part for the job. All the candidates
either have too low I_OUT, self-protect themselves like Jackie Chan with
various hiccup/latch off algorithms or require so many external
components that it is hard to distinguish them from a discrete solution
(the notorious LTC...). And the remaining few ones don\'t have legs,
which excludes them from the BOM.

Do you know of something as simple as TPS54302 which would just start
pumping current when overloaded? The limit value can be very rough; I
don\'t care. Or do I really need to roll my own old-school truly
hysteretic converter based on the INA293 or compatible and a bunch of
comparators?

There is a Linear Technology design which has two of their linear
regulators (LT1086 I think) preceded bij switcher pre-regulator,
which is set to keep de voltage over the linears constant (1.7 V or
so) . The linears do the actual current limiting an regulation, it
could go down to 0 V. I don\'t have the pdf or link handy, but I
recall they have a small pcb with everything on it, I think it was
named \"lab supply\".

Mat Nieuwenhoven

 

[Mat Nieuwenhoven]

On Thu, 16 Jul 2020 09:55:30 +0200, Piotr Wyderski wrote:

Hi,

I need a simple synchronous buck converter capable of seamless CV/CC
transition. V_IN_MAX=17V, I_OUT=3-5A (roughly), V_OUT=3V. I had googled
a lot but was unable to find a nice part for the job. All the candidates
either have too low I_OUT, self-protect themselves like Jackie Chan with
various hiccup/latch off algorithms or require so many external
components that it is hard to distinguish them from a discrete solution
(the notorious LTC...). And the remaining few ones don\'t have legs,
which excludes them from the BOM.

Do you know of something as simple as TPS54302 which would just start
pumping current when overloaded? The limit value can be very rough; I
don\'t care. Or do I really need to roll my own old-school truly
hysteretic converter based on the INA293 or compatible and a bunch of
comparators?

There is a Linear Technology design which has two of their linear
regulators (LT1086 I think) preceded bij switcher pre-regulator,
which is set to keep de voltage over the linears constant (1.7 V or
so) . The linears do the actual current limiting an regulation, it
could go down to 0 V. I don\'t have the pdf or link handy, but I
recall they have a small pcb with everything on it, I think it was
named \"lab supply\".

Mat Nieuwenhoven

 

[Mat Nieuwenhoven]

On Thu, 16 Jul 2020 09:55:30 +0200, Piotr Wyderski wrote:

Hi,

I need a simple synchronous buck converter capable of seamless CV/CC
transition. V_IN_MAX=17V, I_OUT=3-5A (roughly), V_OUT=3V. I had googled
a lot but was unable to find a nice part for the job. All the candidates
either have too low I_OUT, self-protect themselves like Jackie Chan with
various hiccup/latch off algorithms or require so many external
components that it is hard to distinguish them from a discrete solution
(the notorious LTC...). And the remaining few ones don\'t have legs,
which excludes them from the BOM.

Do you know of something as simple as TPS54302 which would just start
pumping current when overloaded? The limit value can be very rough; I
don\'t care. Or do I really need to roll my own old-school truly
hysteretic converter based on the INA293 or compatible and a bunch of
comparators?

There is a Linear Technology design which has two of their linear
regulators (LT1086 I think) preceded bij switcher pre-regulator,
which is set to keep de voltage over the linears constant (1.7 V or
so) . The linears do the actual current limiting an regulation, it
could go down to 0 V. I don\'t have the pdf or link handy, but I
recall they have a small pcb with everything on it, I think it was
named \"lab supply\".

Mat Nieuwenhoven

 

[Mat Nieuwenhoven]

On Fri, 17 Jul 2020 08:52:57 +0200 (CES), Mat Nieuwenhoven wrote:

On Thu, 16 Jul 2020 09:55:30 +0200, Piotr Wyderski wrote:

Hi,

I need a simple synchronous buck converter capable of seamless CV/CC
transition. V_IN_MAX=17V, I_OUT=3-5A (roughly), V_OUT=3V. I had googled
a lot but was unable to find a nice part for the job. All the candidates
either have too low I_OUT, self-protect themselves like Jackie Chan with
various hiccup/latch off algorithms or require so many external
components that it is hard to distinguish them from a discrete solution
(the notorious LTC...). And the remaining few ones don\'t have legs,
which excludes them from the BOM.

Do you know of something as simple as TPS54302 which would just start
pumping current when overloaded? The limit value can be very rough; I
don\'t care. Or do I really need to roll my own old-school truly
hysteretic converter based on the INA293 or compatible and a bunch of
comparators?

There is a Linear Technology design which has two of their linear
regulators (LT1086 I think) preceded bij switcher pre-regulator,
which is set to keep de voltage over the linears constant (1.7 V or
so) . The linears do the actual current limiting an regulation, it
could go down to 0 V. I don\'t have the pdf or link handy, but I
recall they have a small pcb with everything on it, I think it was
named \"lab supply\".

I found the
pdf:
https://www.analog.com/media/en/technical-documentation/tech-articles/
lt-journal-article/LTJournal-V24N2-02-df-BenchSupply-Szolusha.pdf

It is 3A, has brick-wall current limiting so no foldback or on-off as
far as I can see.

Mat Nieuwenhoven

 

[Mat Nieuwenhoven]

On Fri, 17 Jul 2020 08:52:57 +0200 (CES), Mat Nieuwenhoven wrote:

On Thu, 16 Jul 2020 09:55:30 +0200, Piotr Wyderski wrote:

Hi,

I need a simple synchronous buck converter capable of seamless CV/CC
transition. V_IN_MAX=17V, I_OUT=3-5A (roughly), V_OUT=3V. I had googled
a lot but was unable to find a nice part for the job. All the candidates
either have too low I_OUT, self-protect themselves like Jackie Chan with
various hiccup/latch off algorithms or require so many external
components that it is hard to distinguish them from a discrete solution
(the notorious LTC...). And the remaining few ones don\'t have legs,
which excludes them from the BOM.

Do you know of something as simple as TPS54302 which would just start
pumping current when overloaded? The limit value can be very rough; I
don\'t care. Or do I really need to roll my own old-school truly
hysteretic converter based on the INA293 or compatible and a bunch of
comparators?

There is a Linear Technology design which has two of their linear
regulators (LT1086 I think) preceded bij switcher pre-regulator,
which is set to keep de voltage over the linears constant (1.7 V or
so) . The linears do the actual current limiting an regulation, it
could go down to 0 V. I don\'t have the pdf or link handy, but I
recall they have a small pcb with everything on it, I think it was
named \"lab supply\".

I found the
pdf:
https://www.analog.com/media/en/technical-documentation/tech-articles/
lt-journal-article/LTJournal-V24N2-02-df-BenchSupply-Szolusha.pdf

It is 3A, has brick-wall current limiting so no foldback or on-off as
far as I can see.

Mat Nieuwenhoven

 

[Piotr Wyderski]

Phil Hobbs wrote:

For my Class H TEC driver, I just dork the feedback pin with another
resistor to a DAC.  You ought to be able to do the same thing with an op
amp to make a CC mode, if your switcher isn\'t too whizzy.

After more research, I believe it is the simplest solution. TPS54302
looks dumb enough; mainly, it seems not to have the output under-voltage
\"protection\". It should be then possible to fool it sufficiently to get
CC mode with a low-side sensing opamp.

I am literally shocked by my findings. Most of my effort goes into the
battle with the \"intelligence\" of the \"modern\" parts, not into the
actual design. What has happened to the predictability of our designs?
Now I have crystal clear understanding of JL\'s pervy art of blowing
parts. I used to attribute it to curiosity, but it actually is a
survival strategy.

Best regards, Piotr

 

[boB]

On Thu, 16 Jul 2020 09:55:30 +0200, Piotr Wyderski
<peter.pan@neverland.mil> wrote:

Hi,

I need a simple synchronous buck converter capable of seamless CV/CC
transition. V_IN_MAX=17V, I_OUT=3-5A (roughly), V_OUT=3V. I had googled
a lot but was unable to find a nice part for the job. All the candidates
either have too low I_OUT, self-protect themselves like Jackie Chan with
various hiccup/latch off algorithms or require so many external
components that it is hard to distinguish them from a discrete solution
(the notorious LTC...). And the remaining few ones don\'t have legs,
which excludes them from the BOM.

Do you know of something as simple as TPS54302 which would just start
pumping current when overloaded? The limit value can be very rough; I
don\'t care. Or do I really need to roll my own old-school truly
hysteretic converter based on the INA293 or compatible and a bunch of
comparators?

Best regards, Piotr

Check out the Rohm BD9E302EFJ Not quite 3.5 amps but 3.0 amps
anyway... Close.

7.0V?28V Input, 3A Integrated MOSFET Single Synchronous Buck DC/DC
Converter

 

[boB]

On Thu, 16 Jul 2020 09:55:30 +0200, Piotr Wyderski
<peter.pan@neverland.mil> wrote:

Hi,

I need a simple synchronous buck converter capable of seamless CV/CC
transition. V_IN_MAX=17V, I_OUT=3-5A (roughly), V_OUT=3V. I had googled
a lot but was unable to find a nice part for the job. All the candidates
either have too low I_OUT, self-protect themselves like Jackie Chan with
various hiccup/latch off algorithms or require so many external
components that it is hard to distinguish them from a discrete solution
(the notorious LTC...). And the remaining few ones don\'t have legs,
which excludes them from the BOM.

Do you know of something as simple as TPS54302 which would just start
pumping current when overloaded? The limit value can be very rough; I
don\'t care. Or do I really need to roll my own old-school truly
hysteretic converter based on the INA293 or compatible and a bunch of
comparators?

Best regards, Piotr

Check out the Rohm BD9E302EFJ Not quite 3.5 amps but 3.0 amps
anyway... Close.

7.0V?28V Input, 3A Integrated MOSFET Single Synchronous Buck DC/DC
Converter

 

[boB]

On Fri, 17 Jul 2020 14:16:49 -0700, boB <boB@K7IQ.com> wrote:

On Thu, 16 Jul 2020 09:55:30 +0200, Piotr Wyderski
peter.pan@neverland.mil> wrote:

Hi,

I need a simple synchronous buck converter capable of seamless CV/CC
transition. V_IN_MAX=17V, I_OUT=3-5A (roughly), V_OUT=3V. I had googled
a lot but was unable to find a nice part for the job. All the candidates
either have too low I_OUT, self-protect themselves like Jackie Chan with
various hiccup/latch off algorithms or require so many external
components that it is hard to distinguish them from a discrete solution
(the notorious LTC...). And the remaining few ones don\'t have legs,
which excludes them from the BOM.

Do you know of something as simple as TPS54302 which would just start
pumping current when overloaded? The limit value can be very rough; I
don\'t care. Or do I really need to roll my own old-school truly
hysteretic converter based on the INA293 or compatible and a bunch of
comparators?

Best regards, Piotr



Check out the Rohm BD9E302EFJ Not quite 3.5 amps but 3.0 amps
anyway... Close.

7.0V?28V Input, 3A Integrated MOSFET Single Synchronous Buck DC/DC
Converter

Re. CV/CC

Typically, voltage feedback is given back to the chip but you could
certainly send it a current feedback signal or combination with extra
ciruitry.

 

[boB]

On Fri, 17 Jul 2020 14:16:49 -0700, boB <boB@K7IQ.com> wrote:

On Thu, 16 Jul 2020 09:55:30 +0200, Piotr Wyderski
peter.pan@neverland.mil> wrote:

Hi,

I need a simple synchronous buck converter capable of seamless CV/CC
transition. V_IN_MAX=17V, I_OUT=3-5A (roughly), V_OUT=3V. I had googled
a lot but was unable to find a nice part for the job. All the candidates
either have too low I_OUT, self-protect themselves like Jackie Chan with
various hiccup/latch off algorithms or require so many external
components that it is hard to distinguish them from a discrete solution
(the notorious LTC...). And the remaining few ones don\'t have legs,
which excludes them from the BOM.

Do you know of something as simple as TPS54302 which would just start
pumping current when overloaded? The limit value can be very rough; I
don\'t care. Or do I really need to roll my own old-school truly
hysteretic converter based on the INA293 or compatible and a bunch of
comparators?

Best regards, Piotr



Check out the Rohm BD9E302EFJ Not quite 3.5 amps but 3.0 amps
anyway... Close.

7.0V?28V Input, 3A Integrated MOSFET Single Synchronous Buck DC/DC
Converter

Re. CV/CC

Typically, voltage feedback is given back to the chip but you could
certainly send it a current feedback signal or combination with extra
ciruitry.

 

[boB]

On Fri, 17 Jul 2020 14:16:49 -0700, boB <boB@K7IQ.com> wrote:

On Thu, 16 Jul 2020 09:55:30 +0200, Piotr Wyderski
peter.pan@neverland.mil> wrote:

Hi,

I need a simple synchronous buck converter capable of seamless CV/CC
transition. V_IN_MAX=17V, I_OUT=3-5A (roughly), V_OUT=3V. I had googled
a lot but was unable to find a nice part for the job. All the candidates
either have too low I_OUT, self-protect themselves like Jackie Chan with
various hiccup/latch off algorithms or require so many external
components that it is hard to distinguish them from a discrete solution
(the notorious LTC...). And the remaining few ones don\'t have legs,
which excludes them from the BOM.

Do you know of something as simple as TPS54302 which would just start
pumping current when overloaded? The limit value can be very rough; I
don\'t care. Or do I really need to roll my own old-school truly
hysteretic converter based on the INA293 or compatible and a bunch of
comparators?

Best regards, Piotr



Check out the Rohm BD9E302EFJ Not quite 3.5 amps but 3.0 amps
anyway... Close.

7.0V?28V Input, 3A Integrated MOSFET Single Synchronous Buck DC/DC
Converter

Re. CV/CC

Typically, voltage feedback is given back to the chip but you could
certainly send it a current feedback signal or combination with extra
ciruitry.