TL431的datasheet里面有source/sink的應用例子,你看看有沒有幫助.

"source" should be 拉電流;
"sink" should be 灌電流.

長見識.學了一招,謝謝

I think maybe you made a mistake.
"source" should be 灌電流;
"sink" should be 拉電流.