I saw these online and they were cheap so I bought some (lot of 20) as filler for my order. I set them aside as I didn't really have an immediate use. Now I do and used them.
At first, I didn't really care as the voltages appear to be fine but during long duration testing, I found that these parts work for a while then suddenly stop functioning for no reason. Time to do some testing.
These are the parts in question.
To the untrained eye, they look legit.
The markings are as follows:
note: The datasheet mentions this is the most premium part which is rated as -40 to +85C operating temp. And it was cheap. Hmmm
They are powered from an 8V regulator and the output is supposed to be near -8V.
It powers two single and two dual op amps so they are not really pushed hard.
They do work but the 10uF ceramic caps I used are making a buzzing noise. They also work fine for a while then suddenly stops oscillating.
This is the screen capture of the one above.
The output is jittery as shown when I turned on the persistence function of the oscilloscope display.
The datasheet says it should oscillate at 10kHz typ. This one is about 2kHz average.
So I did another test and populated another PCB. I took another one from the same tape and did the same test. This one actually works a little better but still makes the buzzing sound.
The frequency is higher but still much lower than the datasheet values.
For verification, I don't have a genuine ICL7660 but I do have a guaranteed genuine LTC1044 which is functionally the same.
The output voltage is higher even when loaded and is operating quietly. This rules out the PCB layout as causing the problem.
Oscillation frequency is lower than the datasheet spec but it is rock solid and the IC does not heat up.
Previously, I have been lucky buying cheap lots of parts but this time I got burned. "You get what you pay for" still applies. Time to find another supplier.
Page created and copyright R.Quan ©06 Mar 2016.