TPS7A49 ultra low noise LDO - trouble

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Hello,

I have a strange behaviour of one of the TPS7A4901 LDO use d in my power supply.

One works as described in the data sheet, the volrtage at the feedback pin is 1,185V; the other has the voltage at the feedback 0.625V.

Everythinf seems OK but the VFB. To have the same regulated voltage I change the value of the resistor toward GND, R22 in the attachment, reducing it of 1.185/0.625 the Vout is exactly as expected.

Why this strange behaviour?
And this is not the first TPS7A49 LDO with this behaviour.

I didn't find anything rumor about this.

Some ideas?

Thanks.
 

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