Is MAX1044 a fragile device ?

[fuzzo]

Hi,

thanks to all of you for these posts !

I see that I'm not the only one complaining about that chip.

In reading your comments I remebered that I always find these DC multipliers and converters odd. I know that some have good results with them but I can't keep wondering , why adding components that can cause injuries and break the circuit ? and these ICs seems to be really picky and fragile.

On the other hand , my snarling dog mold spore has one and I never had a problem with it  . So maybe it's juste a question of power protection and carefully designed circuits.

[R.G.]

They are really not designed to run at over 10.00000000000V.

Some of them, some batches from some manufacturers, may survive better than others. Just as "Italian Creme Cake" tastes different depending on whose recipe was used, who cooked it, where the ingredients were bought, how long it was baked, what temperature, and so on, semiconductor devices are actually made by purifying silicon to some degree, cutting and polishing it to some degree, masking, diffusing, baking, and all the other little processes that have to be tweaked to get semiconductors to semiconduct. Each of those steps is an analog process. Figuratively, there is a person turning the valve on the arsene gas or setting the oven to 800C for two hours, that kind of stuff. There is variation in all manufacturing processes.

The limits on datasheets are set by a manufacturer saying "Well, I'm not going to (knowingly!) ship stuff that won't do at least this good." So some MAN1044s may die at 10.0000001V, and others may not care much up to 12, 15, whatever. Some will die at 10.0000001V at one microamp over the specified currents, but will live to 13V at lower currents.

The moral of this story is that although many devices may work at voltages, currents, or power levels beyond the absolute maximums on the datasheet, it is remarkably silly to think that just because a few devices from one batch did work that way, all of them will always work that way. I've seen engineers fired for specifying stuff beyond the maximums without getting special dispensation to do so because of the risks involved. I've seen "deep sorts" of the ordinary variation of chips to get some special speed or voltage range, when the full, unsorted run of chips from a wafer was available.

A chip that works reliably up to the absolute maximums specified on the datasheet is not fragile. It's normal. A chip that works beyond the absolute maximums listed is interesting, but not an indication about the chip type in general, nor an indication of reliability because when you make one parameter bigger in silicon, you usually sacrifice something else. Hey, wait! That happens a lot in life, doesn't it? 

It's always possible for a weak lot to slip through, just like experienced artillery men will tell you stories about "short rounds".   

The moral of the story is to learn the absolute maximums, do a good job of knowing the variations your product will work in, and design in some margins for yourself. I have had thousands of the MAX1044 in products in customers' hands for about 7 years now, and see only the expected failure rate on them.

If you know or suspect you're going to have problems with a chip rated at 10.0000000000V, either design in some safety circuits, or get a bigger horse.

[ggedamed]

R.G., what about the chip from the YouTube clip on the first page of this thread? It is working at 18V - is it a super-MAX1044?
Hmm, maybe I''ll sacrifice another one in the name of science and see at what voltage it dies in an inverter circuit.

[R.G.]

R.G., what about the chip from the YouTube clip on the first page of this thread? It is working at 18V - is it a super-MAX1044?
Hmm, maybe I''ll sacrifice another one in the name of science and see at what voltage it dies in an inverter circuit.

There are other chips, including pin-for-pin compatible ones, which do work at higher voltages. The ... um? 7662, 7660S, LT1054, maybe others.

The LT1054 is pretty good at higher voltage and currents.

[ggedamed]

Hmm, maybe I'm not that good at explanations. It was me and a MAX1044 in the clip. I tested 3 in the voltage doubler configuration at 18V and they lived. I tested one in inverter configuration at 18V and it died.

[R.G.]

I suspect that the voltages on the chip itself are different in the doubler versus inverting configuration.

[armdnrdy]

Hmm, maybe I'm not that good at explanations. It was me and a MAX1044 in the clip. I tested 3 in the voltage doubler configuration at 18V and they lived. I tested one in inverter configuration at 18V and it died.

In the data sheet Maxim shows different purposes and configurations of how the MAX1044 can be used. The max. voltage ratings that they list are across the board for all configurations. I'm sure that it would get confusing if a data sheet listed max. voltage for this configuration and max voltage for that configuration.

I have never used a MAX1044 because by the time I started building pedals, everyone had already tested these charge pumps for me.    

I have read too many posts on the net of how these chips failed. I use the LT1054CN. This is a much more versatile charge pump! As R.G. stated, The LT1054 is pretty good at higher voltage and currents.

[Jdansti]

From the datasheet:
http://datasheets.maximintegrated.com/en/ds/ICL7660-MAX1044.pdf

General Precautions
1) Connecting any input terminal to voltages greater than V+ or less than ground may cause latchup. Do not apply any input sources operating from external supplies before device power-up.
2) Never exceed maximum supply voltage ratings.
3) Do not connect C1 and C2 with the wrong polarity. [See datasheet]
4) Do not short V+ to ground for extended periods with supply voltages above 5.5V present on other pins.
5) Ensure that VOUT (pin 5) does not go more positive than GND (pin 3). Adding a diode in parallel with C2, with the anode connected to VOUT and cathode to LV, will prevent this condition. [See datasheet].

[armdnrdy]

That's a lot of "Do not's"

I prefer data sheets that say: You can also do this, and if you add this component it has this feature as well!

I just breezed through the T.I. LT1054 data sheet. I couldn't seem to find the "Do not list"

[Jdansti]

I don't know if any of those rules apply to your situation. I was hoping that list would make me sound smart.   

If I were going to use a 1044, I think would use a 9V Zener to protect it.



My rough guess is that R would need to be 10 Ω - 20 Ω.

[armdnrdy]

I believe that Midwayfair mentioned that in the beginning of this thread.

Not a bad idea if somebody was holding me at gunpoint demanding that I use a MAX1044 or be killed! 

Other than that, I guess if you had a stock of them and needed to use them up the zener would be the way to go.

I personally have never read about anyone having problems with the LT1054, so I'm kind of sold on that one.

I was using the TC962CPA but it had a frequency downfall. The frequency runs at 12kHz with a frequency doubling option. I've had whine problems with these that I couldn't whip!

The LT1054 runs at 25kHz with a frequency adjustment as well. This can be adjusted well above the audible range. (at least for humans! Bats may be unhappy but what are you going to do? What's that old saying? You can please some bats some of the time but you can't please.... 

[slacker]

ggedamed, what load do you have on the output of the chip, how much current is it drawing?
Perhaps it can survive 18 Volts at very low current.

[ggedamed]

In the clip it had a 2k7 resistor as load. At 35V output it would make almost 13mA.

It is still on the breadboard so, when I'll have some spare time, I'll try again with a 1k8 resistor to go to the maximum recomended current of 20mA. If it survives I'll put it in the inverter configuration and raise the voltage until it dies. It's time to some serious science experiments . I just wish somebody could confirm/infirm my findings.

[DDD]

I have a bad experience with the MAX1044 in guitar stompbox.
It's very sensitive to voltage overloads (even short peaks) as well as to the current overloads at the initial ON moment (inrush current).
I've installed LT1054 instead of MAX1044 and it's OK.
*** LT1054 is some times more expensive than MAX1044

[lowbrow]

The 7660SCPA is both better and cheaper. You can buy them in bulk off eBay. About $14 for fifty. It's a drop in replacement for the 1044.