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We have 100 LM431CCM3 which oscillate.
And 5 LM431CCM3 from another production lot which are stable.
Cathode Current 10mA
Load Cap. 1nF
The load is a ceramic cap 1nF and nothing else.(usually a ref input of an ADC, but that makes no difference, tested!)
According to the datasheet the design should be fine and STABLE!
Shouldn't it be stable between 10pF and 10nF?
Any ideas why this happens?
Kai,
Regards,
Josh
Supply voltage is 5V and Vref is 2,5V.
Yesterday I build up the circuit without a pcb, only the parts and short copper wires and 100nF across 5V.
It oscillates!
And additionally the formerly good five LM431 can oscillate too!
Not so much as the new prodction lot, but sometimes they'll start when I apply VCC 5V.
The question is no more, why I have good and bad parts.
It is, why do all LM431 show a tendecy to oscillate with 1nF?
