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LMZ20502: LMZ20502 1.2V output issue

Part Number: LMZ20502
Other Parts Discussed in Thread: TPS82084, ,

Dear Sir,

In fact I used TPS82084 in my previous design, it work well .because it cannot be bought in stock recently, I have to use LM20502 instead. but I forgot add Cff in my design.  the fig is just like this:

Vin is 5V, Cin and Cout is 22uf, both of Rfbt and Rfbb are 40.2K. Vout should be 1.2V  , but Cff is forgot to place.

I measure the Vout,   about 0.89 V

So, I have some question:

1: Cff is necessary for this LMZ20502 usage? the real output is about 0.89V,   it is so smaller than 1.2V expected.  can this Cff impact on it?

2: Can 47pf cap be used ?  the suggested value is 20 pF。

3. Cout is 22uf, the suggested value is 10uF, can 22uF be used for Cout?

Best regards.