[Rumgucker]

...ich mir auch nicht wirklich...

[voltwide]

Huhu, Chris, gib mal Laut!

[christianw.]

Was soll ich sagen, wir sind wieder da, wo wir aufgehört haben.

Kannst du mir eventuell die Bilder vom Oszi per Email senden? Dann schicke ih die gleich weiter zu Maxim.

In der Zwischenzeit kannst du ja mal ein paar LS anschliessen. Man könnte natürlich auch mal die Filter bestücken.

Bei mir fängt gerade das Semester an, somit bin ich ein bischen beschäftigt.

[voltwide]

Lade Dir doch das img von #65 runter, was anderes Interessantes habe ich bislang nicht zu bieten.

[christianw.]

Zitat:> |================================================================
> | Staff Comment 2012-10-01 09:00:07 PST
> | By: Matthew M
> |
> | Hello Christian,
> |
> | I want to apologize for the delayed response. We no longer make
> | MAX9704 evaluation kits so I had to retrofit a MAX9714 evaluation
> | kit to be suitable for this device.
> |
> | Now that I have a working board, I have booked some lab time in
> | the coming days to take a look at this device at start-up, and I
> | will report my findings as soon as is possible.
> |
> | I appreciate your patience,
> |
> | Matthew Mowdy
> | Audio Applications Engineer

Meine direkte Antwort mit Voltwides Bild:

Zitat:Hello Matthew,

thanks for your efforts. We measured Board 1 another time with "ultra low ESR capacitors", does not make much difference. Even with /SHDN pulled low, it looks like the picture attached.

It is clearly seen that the current drawn is not only caused by the bulk capacitors.

Yellow line is voltage directly on supply, blue line is current via 0R33. So there is some current (1A+) flowing somewhere.

For this measure, no load where connected.

Regards,


Christian

[voltwide]

ja, da bin ich ja mal gespannt....

[christianw.]

Zitat:|================================================================
| Staff Comment 2012-10-01 10:28:24 PST
| By: Matthew M
|
| Hello Christian,
|
| I will produce a similar plot using my kit for comparison once I
| get a chance to get onto the lab bench. Thanks for the update.
|
| Matthew Mowdy
| Audio Applications Engineer

[christianw.]

Zitat:|================================================================
| Staff Comment 2012-10-04 15:56:50 PST
| By: Matthew M
|
| Hello Christian,
|
| I have now had some time to experiment with sequencing this part.
| I used a MAX9714 evaluation kit with a
| AX9704 mounted on it. I matched your configuration (spread
| spectrum, maximum gain, 12V supply) in order to best simulate
| your situation.
|
| To avoid introducing impedance between the device and the
| supply/bypass capacitance I used a current probe to create my
| plots. I am a bit concerned that the 330mΩ resistance could be
| part of the problem. Is it always present between the supply and
| device and where is it located relative to the supply, bypass,
| and device?
|
| The reason I am concerned is that I don't see nearly the inrush
| current you do. When you power up, what is the state of the Input
| pins (INL±/INR±)? A thought occurred to me - maybe your setup
| draws so much power because you have active inputs on power up.
| My concern is that if the inputs are active when the part is
| inactive, and then the device is powered, this could damage the
| device.
|
| The proper sequencing should be:
| 1. supply powers up, device may come out of shutdown during this
| if the /SHDN pin is supply referenced (always on operation).
|
| 2. take the device out of shutdown (may happen in step 1).
|
| 3. Apply an input analog signal. These inputs (INL±/INR±) are
| best left off until the device is fully powered, and the turn on
| time (EC table, page 2) has elapsed.
|
| I will next post my power-on screen shots.
|
| I found that I had exactly the same start-up waveform regardless
| of if I powered the supply with the device held in shutdown, or
| powered with shutdown tied to the supply (so the device activated
| on power-up). In all cases (INL±/INR±) are not driven during
| power on. I drew the same inrush current (1) with a without a
| load (my load was 8Ω + 68µH).
|
| I then tried again with the device allowed to power up active
| (/SHDN goes high with the supply, like your case). The current
| draw was the same (2) as with the device in shutdown. The
| difference was that about 80ms later the output began switching
| (purple line, 3).
|
| In all cases the initial power up draws a peak of about
| 200-210mA.
|
| dark blue = supply (12V)
| light blue = current draw (mA)
| purple = Single ended output, used to show when switching starts.
|
| 1. PU_12V_SHUTDOWN.bmp
| Power up with the device held in shutdown. This was identical
| loaded or unloaded.
|
| 2. PU_12V_ACTIVE.bmp
| Power up with the device coming out of shutdown as the supply
| rises. This also was identical loaded or unloaded.
|
| 3. PU_12V_ACTIVE_SWITCHING_START.bmp
| Same as number 2, but longer time scale allows the timing of when
| output switching starts to be seen.
| I ran out of space in the previous. I tried checking the
| switching as well with and without a load. In both cases the
| single ended outputs switched from ground to 12V. This was
| regardless of load. I didn't see any case where the switching was
| outside of the supply The maximum differential voltage is
| therefore +12V (positive output high, negative low) to -12V
| (positive low to negative high) as expected. This leads to the
| speaker never having a differential voltage of more than 12V
| across it at any time. Again I did not see a difference loaded or
| unloaded. With no input signal, the only bias on the speaker
| output should be when the switching is slightly faster or slower
| on the positive or negative output.
|
| Finally to test survivability, I automated a supply sequence that
| power cycled the device thousands of times. After running over
| night with several thousand cycles the device is still running
| fine with pout any apparent ill effects.
|
| I cannot reproduce your issue unfortunately, and i am at a loss
| to explain it as I simply do not see the large inrush current you
| do (looking at your last figure, if the sense is 0.33Ω, and the
| spike is about 8V across the resistor, thats over 2A of inrush!).
| The possibilities I can come up with are:
|
| 1/ The sense resistor itself is a problem, or the impedance /
| inductance between the device, the bypass, and the supply is too
| high. Remove the sense resistor, and try with a current probe and
| the minimized impedance on the supply bus.
|
| 2/ The device is being powered with a signal already present at
| the input. Do not drive audio through the amplifier until it is
| fully powered up to avoid any chance of latch-up, etc.
|
| 3/ Other external components are not specified correctly or are
| damaged. You did find bad bypass caps, perhaps some other
| components are damaged, or are not rated correctly for the
| operating range of the device. Check the MAX9714 EV-kit build of
| materials against your own for component specification mismatches
| (not just values but voltage and power ratings for components).
|
| 4/ The parts themselves were already damaged or have problems.
| Where did you get these devices? Did you order or sample them
| through Maxim direct or one of our authorized distributors? What
| was your source and do you still have the purchase order
| documentation available? Normally I would not worry about
| counterfeits, but the behavior your observing is vastly
| different.
|
| Outside of this, I am out of ideas for the moment. I may be able
| to schedule some additional lab time early next week to dig a bit
| deeper, and follow-up on your responses.
|
| Again, thank you for your patience and I do apologize for the
| delayed response.
|
| Matthew Mowdy
| Audio Applications Engineer

PU_12V_ACTIVE.BMP
[IMG] https://stromrichter.org/d-amp/content/i...ACTIVE.png[/IMG]

PU_12V_ACTIVE_SWITCHING_START.BMP


PU_12V_SHUTDOWN.BMP

[Rumgucker]

Der hat ja richtig geackert...

Tja.. dann mal ran mit der Stromzange

[christianw.]

Sowas tolles habe ich leider nicht.

Ich bin allerdings auch mit meinem Latein am Ende, wo da das Problem liegen sollte.

Ich sende ihm zumindest erstmal die Batchnummer der Bestellung rüber.

Wenn sich das Problem nur mit meinem Layout reproduzieren lässt, muss ja iweo nen Fehler sein, den wir bis dahin übersehen haben. Ich checks nicht.

[Rumgucker]

Vielleicht sollten wir uns Dein Layout noch einmal gaaaanz genau anschauen?

---------

Stromzange will ich auch haben. Fixfertige Geräte kosten nur noch rund ? 50. Und uns würde ja ne Stromzange als Vorsatz fürs Scope reichen. WIr brauchen das ganze Display und Schalter und Buchsengetüddel nicht.

[christianw.]

Hajo.

Layout angucken:




Ich änders es mal auf den Ist-Zustand, betrifft ja nur den Pull-Up-C.

[voltwide]

Also ich habe hier das Layout von Chris, und konnte auch nichts Verdächtiges entdecken. Gemessen mit 3x 1Ohm Metallfilm in der Masseleitung.

Bevor ich 50? für ne "Stromzange" einplane, ist ein Blick auf die Specs angesagt. Die üblichen Stromzangen sind für 50Hz Wechselströme vorgesehen. Die haben meines Wissens nur wenige kHz Bandbreite.

Ich habe hier eine R&S Stromzange, die geht bis 30MHz, -
fängt aber erst bei 9kHz an.

Ansonsten: Selber bauen, mit einem hochpermeablen Ringkern.
50Wdg draufwickeln.
Mit 50 Ohm abschließen.
Ergibt 1Volt/1Amp auf dem Scope.

[christianw.]

Und das funktioniert auch mit DC?

[Rumgucker]

Ne. Natürlich nicht. Volti denkt in die falsche Richtung.

[Rumgucker]

Ich muss mich ürbigens korrigieren...

? 20,-- (sonst hätte es mich ja wohl kaum interessiert... )

http://www.reichelt.de/Zangenmessgeraete...nr=UT+202A

[Rumgucker]

Zitat:Original geschrieben von christianw.
Layout angucken:

Ich guck....

[christianw.]

Hmm, die Zange kann aber auch nur Iac.

[Rumgucker]

Ich versteh Pin11 nicht. Entweder liegt der auf ganz high oder auf dem Regulator. Aber wird er eigentlich auch mal nach PGND gezogen?

[Rumgucker]

Zitat:Original geschrieben von christianw.
Hmm, die Zange kann aber auch nur Iac.

Hups... Du hast Recht