Two VITAL, Current Sensing pages w/in device data-sheet have, "gone missing" ... greatly interest our (large) client + MANY here!

Hi,

The reason we didn't include these 2 applications is because we are planning to update the application with some more information in a separate application note. As of now we do not have a firm date as to when this will be released but hopefully sometime later this year. Also we do not suspect any errors in the application info on these pages but we do recommend to thoroughly evaluate the circuit before using it in your design. Sorry for the inconvinience this might have caused.

Rabab Itarsiwala said:

we didn't include these 2 applications is because we are planning to update the application with some more information in a separate application note.

Thank you - appreciated.

Yet - our large clients (well) note that those "excised" 2 pages appear the (only) pages completely removed!   And that was done in/around 2012 - it is (now) 2016 - that's a huge time-gap - is it not?

While "Planning to Update" may (sometimes) make sense - why would that key/critical data be deleted?   How can that (ever) make (any) sense?

Does your "suspicion" of "no errors" include the crystal clear point I raised - specifically the direct connection of Motor Supply to Vin(-) - not to Vin(+)?  

May we ask, "How that suspicion" was formed?   (one hopes - that as (your) team has had four years to devise an App Note - you could do better than "suspicion!")

Hi,

Hope you are having a great evening. 

1. The datasheet update was done in May 2015 (9 months ago - not 4 years). Attached are the two versions. Version B (Revised 2012 - still include App information). Version C (Revised May 2015 Current version - those two apps circuits were removed.)

2. TI policy establish that we need to send notifications to customers if we change sections of the datasheet that affects the device performance. This is not the case, for this reason there was not a PCN for any customer. Anything that is application information is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

3. Related to the question about the polarities of the circuit - We believe it should be ok to use it the way shown, except that the ouput will be of opposite polarity. If you switch the top inputs then you will need to switch the inputs of the bottom amplifier as well.

Hope this helps clarify your questions. I am attaching older datasheet so customer can use as reference for those two applications. Again, your customers should validate and test their design implementation to confirm system functionality.

ina282C - Copy.pdfsbos485b.pdf

Regards,

Mayrim Verdejo said:

Hope you are having a great evening. 

Really - with this posting recording over 300 visits/views w/in its first 10 hours of existence - is (hope) for my evening proper?   (somehow - neither client nor I -bask in the (intended) warmth of that opening...)

That said - both client & my firm are glad that you've responded.

My role is to assist the client in the discovery  - and proper utilization - and then "design-in" of tech devices.    This client expressed concern - asked for my intervention/assistance - such explains my arrival.   My goal is to, "Fill the client's sockets" with devices which "best meet" each client's "need matrix."

Now we note that the client's document differs from the one you sent - and their report to me was what I presented, here.   Note too that I requested tech assistance in this matter nearly a week ago - and received response essentially duplicating that (earlier) posted here.   (which was (clearly) unacceptable to our large client)

Your post steers hard to vendor policy - which is outside of the "clear usage and value proposition" of the INA28x device - which I took pains to convey.   (at the firm's direction - btw.)

It remains highlighted that those 2 key/critical pages - and likely (only) those 2 key/critical pages - were deleted.   And that remains unexplained!   And the claim that a new App Note is "underway" is in no way sufficient justification for "excising" High-Value data - is it?    

That specific and limited excising is profoundly curious - is it not?    And (still) unanswered!  

Yes it is your right - yet does it invoke confidence - at all?    (I can convincingly report that it does not - especially to a client w/EAU potential in excess of 500K -1M5 (real) units...)

Having past co-founded - then taken tech firm public - I note that "Comfort & Convenience" prove crucial - especially in critical device selection.   The (still) unexplained "pull" of key/critical data breaches both comfort & convenience - and may not prove to your best interest...

It remains w/in your power to calm this concern - client would greatly appreciate this cooperation...

Hi Mayrim,

From our perspective experimenting last year and presently with INA282 in motor drive current sensing. We found the documentation was/still is missing clearly illustrated current directions across the shunt relative the provided output step response figures. The transient response figures assume only that (V+IN minus V-IN) and negates the reverse direction entirely. Actual current direction depicted by an (arrow) has been replace by the word (Load) and a step response table that does not always concur with shunt input polarity when the load is referenced to ground.

Other wise as you advised CB1 the output becomes inverted. Yet from a shunt (Load) perspective sensing what seems the only proper configuration measures reverse current from ground traversing B+ or (V-IN) is crowned the (Load) from a ground perspective. That is not fully disclosed in the transient response figures and can lead to improper connects of the shut inputs relative to B+ power supply location noted as (Fig 38) -14v to +70v. Now missing in the datasheet (May 2015) said motor drive illustration and circuit replaced by a nice differential and summation scope captures, are very much appreciated.

Regarding the missing pages depicting low side totem pole current monitor placement:
Our more recent find by reversing (-IN) for (+IN) gives entirely different step response output behavior relative to either forward or reverse current direction across the shunt. For low side only current measures the INA output step response performs entirely different (better) from a ground perspective or load (V-IN) versus the opposite (V+IN). Otherwise it seems the output step response follows shunt current in both directions when (V+IN) is relative to ground and a center output reference is set.

This content was removed from the data sheet in accordance with our internal directives.  New content and new products will be out this year focusing on in-line motor control, but it is not ready yet as the products are not ready yet.

If you have further questions about this topic, please contact me at bridgmon_jason@ti.com.

Jason,

In my short time here I've (already) read/reviewed (many) of your postings.   Giant & my firm are delighted that you've arrived.

I've been fortunate to attend Engineering, Business & Law School - and in each case we were taught to avoid, "Over Promise - and Under Delivery!"   The claims for the "Phase Current Equivalency" achieved by the dual INA282s are ripe w/promise - are they not?   And then "pulled" with NO explanation...

And - even with the time/effort I expended here - we could not restore (any) confidence in the claims carried w/in those 2 "disappearing" tech pages.

Our large client - capable of massive volume buys - is hugely discomforted by the unexplained removal of those 2 pages.   And - when I questioned that unexplained page removal here - in the attempt to gain the clarity required to, "Drive towards a large Sale" - the dual vendor responses were found hugely inadequate.

I should add that my consulting firm is often chosen to assist clients in the discovery of the optimal design & product solution - which is unlikely to come from any "Single Vendor source."   Our firm - not being bound by (or to) any individual vendor - is thus free to survey and suggest from a vast field of devices.   Our client did not wish to involve the cadre of FAEs which currently service - of course that's their right - and explains my postings, here...

If you'd enable your PM/Conversations - I'd be delighted to engage you - and try to resolve this unexplained page removal - which has caused such great concern.

Thank you for noting this post - which appears to have, "Touched some nerve" as the 2-3 day view/visit count approaches 1K!   One hopes this level of interest can drive this issue to proper completion - and I'd be only too glad to report a successful outcome - right here!

I believe I explained why we removed the pages. Perhaps you could provide some information about your client's application so we can review it and help them make a decision on an appropriate product with confidence.

Please - what do you think the unexplained removal of 2 key/critical pages does to, "Volume User" Confidence?   And why (only) those 2 pages?

I removed the claimed "Suggested Answer" as client and I remain severely discomforted by the (still) unexplained removal of (only) those 2 key/critical pages!   Such suggests something of grave concern - does it not?   If not - why then ONLY the Removal of those 2 pages of critical interest to our client?

Confidence continues to plunge - providing (yet more) information - when our simple & direct question remains unanswered makes NO sense!

When you look at figure 42 from the “missing 2 pages,” the resistor you’ve highlighted in orange is where most customers want to put the INA28x current shunt amplifier. If you read the text, you’ll find that we are not recommending this placement in all cases, just showing that it exists. You’ll see we say this in the NOTE, “…due to the common mode transients that even the best amplifiers do not reject completely.” If you are operating sufficiently slowly and can allow the output to settle after a common mode step before you sample it, then you can use the INA28x with good confidence in the phase current sense position. Most customers operate faster than that. For those customers, we recommend the high side or low side current sense positions because the common modes are constant.

If you are interested, you can see some examples of the transient behavior with large common mode steps in figures 21 to 24 of the data sheet revision released in May 2015. Ultimately, removing these 2 pages disambiguates the data sheet and how the device can be used in a motor control application, which is why we decided to remove them to best serve our customers.

Jason Bridgmon said:

If you read the text

That's more than a bit harsh  - is it not?   Do you honestly believe that I've "not" made major effort - devoted great time/effort/resources - and read every single word?

May I suggest it may "not" be this forum user who has failed to properly read/absorb?   Note (one) here is too diplomatic to suggest that another has, "Not read!"    

Our goal was NOT to use the Phase Sensing Sensor "placement" - as you now introduce - but instead, Employ the method embodied on (now departed) Page 24, Figure 43.  Sensing & Summing Totem Pole Current.     Might you have (somehow) missed that?  

With 1100+ views/visits - and many PM comments from forum users/friends - it's clear that most others "detected" my, "Employ Pg 24 objective"...)

Did I not write here - and highlight - the (past) Page 24, Fig. 43 illustration of TWO INA282 devices - connected to achieve the "benefits" of Phase Sensing - yet avoiding the, "transient, common-mode artifacts" which appear to plague conventional Phase placed, Sensing. 

It was then - and remains now - "STILL UNANSWERED!"  

And so again, "Does Page 24, Fig. 43 fully & properly achieve its (past) written claim?   (marked in mating red - immediately above)

You speak towards the desire to, "Best serve your customers."   Might commenting upon the efficacy of (Pg 24, Fig. 43 diagram) - repeatedly referenced/presented herein - even better - serve your customer?  

Figure 43 of the May 2015 data sheet clearly shows that current differencing produces the expected output. It's real data we captured in a lab with a simulated load.

Jason Bridgmon said:

Figure 43 of the May 2015 data sheet clearly shows that current differencing produces the expected output

May I note - again - that is NOT the question (just) asked!   Could the subject/title of my posting have been any clearer?   We seek clarification of the 2 pages of claims/representations - which have, "Gone Missing!"   That is NOT embodied w/in May 2015 - quite clearly...

Our client has (little) interest in May 2015 data sheet - instead - might you comment upon the question (repeatedly) asked?   Specifically Pg 24, Fig 43 (past data-sheet) - as repeatedly presented - right here?  

It is those claims - and those claims only - which are of interest to our large client!