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Part Number: LM431
i designed a reference voltage for the signal detection with LM431B , the schematic is below:
Because the Cload selection could affect the Vout oscillation , i choose the 1nF for the Vout (remove the 1uF ) , however, i still find the Vout oscillation like below:
In the description of the datasheet, the Vout is in the stable range:
When i replace the LM431B with the TLV431A in the same circuit , the Vout is stable , no oscillation . Please help me what's the reason , thanks!
The stability boundary conditions chart is a typical graph that can vary from device to device and lot to lot.
I cannot recommend to use 1.001uF on the output because it will be in the instability region of both device.
A much smaller much larger cap is recommended. I would check out the app note below to understand stability charts.
While this TL431 might not oscillate, other TL431 can oscillate.
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If you are using the TL431, check out the new ATL431LI for improved system performance in a p2p package or a ultra small X2SON (1mm x 1mm x 0.4mm)
Check out: Voltage Reference Design Tips For Data Converters a new app note that discusses voltage reference error and how it affects ADCs/DACs
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In reply to Marcoo Z:
Thanks for your reply.
Yes, we are currently using the 1nF in the TL431 with no issue . However, i don't know why the oscillation is still existing on the LM431 ?
if this TL431 oscillate and other TL431 can't oscillate , how can we make sure the capacitor is Ok in the mass production stage even it could pass in the evaluation stage.
In reply to Jason Fan:
Can you verify if it is 1nF or 1uF total cap?
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