I have a problem with TL431 voltage reference circuit:
There is no load connected to VREF25.
When I remove C8, voltage VREF25 is perfectly stable 2.5V.
But when I put C8 back into the circuit, voltage VREF25 is oscillating and I can't figure out why:
It is irony because C8 was meant to stabilize VREF25.
UPDATE:
I tried to use capacitor with higher capacitance (470nF). It did not help.
I tried to use resistor (R10) with lower resistance (330Ω) to increase current (from 1mA to 2mA). It did not help.
UPDATE2:
3.3V line is this:
I use genuine TL431 from NXP.
There's no 139kHz signal in my circuit. Actually I disconnected this voltage reference from the rest of circuitry.
I use SMD components, capacitors and resistors are 0805.
Best Answer
According to the datasheet provided, 0.1uF is right at the boundary condition for oscillation (ref. figure 23). Use either a larger or a much smaller capacitance.