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MAX3222's dying

Hi,

We are having unusual failures on MAX3222CPN devices from week

0437. Of 25 installed 6 have failed, generally in the same way. When driving into a weak load (1 transmitter feeding 2 receivers, also 3222's) the high side driver only drives up to 3.0 volts -- the low side driver still drives down to 6.9v. This is a 5v supply system. We don't think there are any unusual voltages being fed back up the line. Capacitors are 3 x 470n and 1 x 100n as per table 2 in the datasheet.

Good/new devices show both high and low levels at approx 6.9v.

A assume these devices have a similar driver to the MAX232 type devices -- has anyone had any failures like this ??

TIA,

Reply to
Gavin Melville
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What do Maxim say ?

Graham

Reply to
Eeyore

I've had a ST3232B die (output pegged, IIRC) on the bench while being plugged and unplugged to various prototypes, I think from something like latchup or ESD. I've resolved to try to stay away from the low voltage *capable* parts, where possible, for a while. It was operating from 5V, as yours, and probably has the same capacitor values or perhaps a bit larger than the minimums).

Is it the chip or a capacitor failure (eg. short)?

Best regards, Spehro Pefhany

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Reply to
Spehro Pefhany

Nothing yet. I also have found it's only one transmitter, and not the other, so that exonerates the charge pump.

Reply to
Gavin Melville

==snip==

No -- the other output, which in service is not connected, works OK. The other subtle problem is that when they fail the link doesn't fail completely. The output high level drops to 3 - 3.05. The high threshold on these devices is around 2.8V (higher than spec'd) and as the charge pump decays slightly the supply drops. The net effect is that short packets (2-3 bytes) get through, but long ones don't.

Sigh.......

Reply to
Gavin Melville

Are you sure you bought the real parts? Maxim warns strongly against counterfeit parts. For instance; Sipex, which clones Maxim parts, is notorious for selling chips with near 100% failure whithin two years.

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Reply to
Nico Coesel

==snip==

I think so -- these all came from Digikey, and Maxim show them as a safe distributor.

Reply to
Gavin Melville

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