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Old 22nd September 2009, 05:19 PM   #11
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yeah jd, not sure how i missed that, guess i was just assuming that LL and RL had to go to ground because that is how most standard pots work.

anyway, I finished my chip and it's working great. The only final complaint I have is a strange sound it makes when powering down LED0 when lowering the volume 20%-0%. Not sure why it does that but I doubt there is much way around it other than not using the LEDs.

Everything else is great though, and I updated the schematic in case anyone should want to use it in the future.

The main change is that you need to add 1uf caps to the input or it will make terribly load pops and clicks when the volume switches are used.

I also included a pic of my chip.
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File Type: png lm4752 with MAX5486 final.PNG (46.2 KB, 318 views)
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Old 28th September 2009, 01:14 AM   #12
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ah fixed the LED0 problem. Just needed to have the LED 5v power separated from the chips power sources (separating the VLogic and VDD voltages makes the chip sound understandably better as well). Also added a ground plane behind the chip which helps as well I'm sure. Now it sounds silent and beautiful
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Old 15th January 2010, 10:50 PM   #13
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Still trying to fix the lockup problem on this chip which is, that withstanding, a fantastic circuit.

Basically when the input reaches the Vpeak ((Vdd+Vss)/2) or clips the circuit goes into a permanent lockup which cannot be undone even with a shutdown or disconnecting Vss. The only way is to disconnect ground or Vdd/Vlogic, i.e. a full power reset.

At least you can make a simple reset button with a general purpose PNP. I attached a schem of what I'm using.

I found that inverting the signal seemed to have helped a lot too. I used an inverting buffer opamp setup as found on ESP over here http://sound.westhost.com/p94a-f3.gif

I'm hoping that a dual supply could help this problem too. Of course increasing supply voltage can help as well but maximum is 6v and recommended seems to be 5.5v

If anyone knows how I could use the ESP project 94A with this chip and somehow integrate the MAX5486 earlier in the sequence before the gain increase that would be great:
Universal Preamp/ Mixer (Part 2)

Ideally I'd like to find a way to put it in line with the inputs and U3. But that messed up the signal too much :/
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Old 6th May 2010, 02:27 PM   #14
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Default Thank you and question re. power supply and reset

Hello,

Thank you, first of all, for detailing out your experience. Its really helpful to those who want to built the same circuit.

A couple of queries...
1. How did you separate the LED 5v power separated from the chips power sources (separating the VLogic and VDD) did you have to use another battery or power supply transformer?
2. Will disconnecting only the Vlogic supply help in resetting IC after a lockup or does the VDD also have to be disconnected?

Thanks in advance,
Max
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Old 17th March 2011, 01:56 PM   #15
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Default MAX5486

Very interesting IC, I would like to make a pre-amp/att PCB only with it and a voltage regulator, probably the tps7a4901. It would receive 9V from the LM317 in the power PCB. tps7a4901 would give noiseless 5.5V.

Who is using this IC?
I pretend use it with VDD=5.5V and Vss connected to GND for single supply operation.
There are 4 power pins: GND, VSS, VDD and Vlogic. Only one GND. I am worried about the noise from the logic part. What can I do to prevent the contamination from the logic operation?

SHDN is is pulled high internally with a resistor to VLOGIC?

Thank you
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Old 27th April 2011, 12:50 PM   #16
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Default MAX5486 Audio IN

The ground of Audio IN in the schematics of this thread is the general ground of the chip.

I thought that the Audio IN ground was the BIAS pin.

Who can clarify?
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Old 26th August 2011, 06:18 PM   #17
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Location: Central Colorado
Default MAX5486 Mode Indicator Output Problem

Hi,

First post on this forum.

I'm using 16 MAX5486's in a project. Everything works well except that the mode indicator output does not get pulled low when the mode pin is toggled with a trailing edge pulse.

I am not using the LED bargraph function so I have all LED pins grounded per instructions. Thinking that might defeat the mode ind LED also, I inserted a one meg resistor from LED 4 to Vlogic. Not only did that not enable the mode ind output, it stopped vol and balance from working.

When I toggle the chip from volume mode to balance mode, it works properly, except of course, mode indicator does not work. The only way to determine which mode the chip is in is to press the buttons. If volume changes, it is in volume mode. If balance changes, it is in balance mode.

No, I have not tried swapping a chip yet. With 16 of these on the board, either all 16 chips are bad (unlikely) or I made the same mistake 16 times (more likely). But since I have spent all of this week troubleshooting and unable to find anything I did wrong, I am stumped.

Yes, I have contacted Maxim tech support. How that work out? I'm here!!

Any advice would be greatly appreciated. I'm even willing to pay someone to look at this device. I'm in central Colorado.

Thanks,

Allen
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Old 28th August 2011, 01:31 PM   #18
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Hey, my first post, too!

As it just so happens, I am breadboarding a prototype for an IR remote based on this chip right now. I am not using the balance feature in my design- its a "wife and kid friendly" remote control for the Dyna amp on my home theater setup so that the regular Directv remote will be able to control volume and power to my amplifier and I decided that the balance mode would simply confuse them...

That being said, its still on a solderless breadboard at this point, so it will be VERY easy to duplicate your scenario. I will try to get to it tonight.

This is probably not relevant to your issue, but there is a major error in the sample schematic on the first page of the datasheet which has been perpetuated on most if not all of the on-line schematics that I have seen for this part. There should actually be TWO bias caps! A 100pf goes between the junction of RL,LL and BIAS and Ground. A 1uF cap goes between BIASCAP and ground. This is correctly described in the text of the datasheet, but the 1uF is unmarked in the schematic and the 100pF is omitted completely. Substituting the 100pF for the 1uF will result in the horrible audio described earlier in this thread.
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Old 28th August 2011, 02:04 PM   #19
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Default I found your problem!

I tried your setup on my breadboard and got the same results. It seems that MODEIND is an open collector output. If you need to read a status from it without using an LED, it will be necessary to add a pull-up resistor between it and VLOGIC. I used a 10K and it works just fine now. Of course, if you do add the LED and its resistor, then it will serve as a pull-up and you will have a nice on-board troubleshooting aid as well...

Al
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Old 29th August 2011, 06:26 PM   #20
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Thank you for looking into my problem! Forums are wonderful things.

Actually, the output is an open drain (same as open collector but uses a FET instead of a transistor.) I was originally using a 10 k pullup resistor to drive downstream logic. But with the difficulties, I switched to a LED and a current limiting resistor, to exactly match the datasheet. Because of the 2.7 volt power supply and a voltage drop across the led of 2.1 volts, it takes a low value of resistor to get a few mils to flow. I started with 2.2k and worked my way down to 100 ohm. The mode output still would not pull low. I tried operating the circuit on five volts. I added the 1 meg resistor to activate the LEDs for the vol/bal meter. I lifted all the LED pins off the circuit board and added resistors and LEDs. If the mute pin is left unconnected (Maxim said it was OK because it has internal pullup) the mode ind output will pull low when the mode input is HELD low. I even have an oscilloscope recording of it doing this. When I tied mute high it stopped working that way, and simply does not work.

I built the exact circuit on a piece of perf board and the mode ind output does not work there either. While I'll admit the mistake could be mine, I am really beginning to believe I have a defective batch of chips. I purchased 100 of them, and have tried others. But considering batch runs can be 100,000 or more chips, the chances of all of mine being from the same batch is slim to none. Maxim tech support was not helpful at all. They kept sending me back to the bench to create scope traces to email them, only so they could think of more things to stall me with. I don't buy millions of their chips so I'm relegated to the bottom-of-the-barrel telephone support staff. I won't even bother with them again, I will redesign the board using another manufacturers chip for volume and balance. I prefer to troubleshoot problems to a resolution, not throw the baby out with the washwater.

I'm bringing in a EE who has Maxim experience this Thursday. But I would sure welcome some communication with you before hand. Please let me know if you would like to do so. My personal email is allendschultz_at_gmail_dot_com. I will call you on my nickel, if that's OK.

Again, thanks for the response. At least now I know that mode-ind works for somebody!!

Allen

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