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TPS7B84-Q1: design principle of TPS7B8401QWDRBRQ1

Lillian Liu(SH)
Expert 3570 points
Part Number: TPS7B84-Q1
Other Parts Discussed in Thread: LM317,

Tool/software:

Hi team,

Is the design principle of TPS7B8401QWDRBRQ1 similar to LM317? Is the output affected by Iadj?

We used LM317 before, 24V to 18V. The Iadj accuracy deviation was large, so we changed to TPS7B8401QWDRBRQ1.

Thanks

Lillian 

  • 0
    TI__Expert 3480 points

    Hi Lilian, 

    In all LDOs with a feedback network of resistor dividers, there is a contribution to VOUT from the FB/ADJ pin current. However, for the TPS7B84-Q1, to ignore the FB pin current error term in the VOUT equation, set the feedback divider current to 100x the FB pin current listed in the Electrical Characteristics table. This setting provides the maximum feedback divider series resistance, as shown in the following equation:

    R1 + R2 ≤ VOUT / (IFB × 100) 

    So the expression for VOUT is:

    VOUT = VFB × (1 + R1 / R2) 

    Best Regards

    Ishaan