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TLV431B: Design check

Part Number: TLV431B
Other Parts Discussed in Thread: TLV431


Please help to check customer question, thanks.

I’d like to use this shunt regulator to create 1.8V from 3.3V, loading of 1.8V is 13mA

Please help to review sch

Is the marked resistor just for current limitation? And is there anything need to pay attention?

  • Hi Lynn,

    the 115R resistor is adjusting the working range of TLV431B. If the load sitting at the 1.8V supply is not drawing any current, the 115R resistor limits the current to 13mA, which is just below the 15mA maximum current recommended in datasheet of TLV431B. This current is mainly flowing through the TLV431B.

    If, on ther other hand, the load is drawing current, then the difference of 13mA and the load current is flowing through the TLV431B. The load current must only increase to a level where still enough current can flow through the TLV431B to maintain regulation. This is 100µA for the TLV431B plus arround 125µA for the programming resistors.

  • Hi Lynn,

    Kai covered this solution well. The resistor R2270 is needed for regulation as it will current limit the circuit to safe level and allow the TLv431 to create a voltage difference from the 3.3V supply so this resistor is necessary.