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Original question:

TIDA-00366: Regarding net VCC_U (VCC_V & VCC_W)

TIDA-00366: Regarding net VCC_U (VCC_V & VCC_W)

Sharat Yadav
Expert 1015 points
Part Number: TIDA-00366
Other Parts Discussed in Thread: TL431

But How TL431 is able to generate 5V as VDD1, since the cathode is connected to 16V(or 15V) wrto U_TOP_REF, while the AMC can take maximum 6mA of current, to have 11Volts drop across resistor R72, it must carry 13.4mA current. Not sure how this is functioning to maintain 5V at the VDD1.

  • 0
    TI__Intellectual 2410 points
    Hi Sharat,

    The forward voltage drop across D12 is ~1V. The voltage at VCC_U with respect to U_TOP_REF will be 15V.

    TL431 behaves like a zener to regulate Vdd1 at 5V. The current through R72 will be ~12mA. The current will remain constant. If the AMC sources a nominal 6mA from Vdd1, then the remaining 6mA will be sunk into TL431. If the AMC sources a maximum of 8.3mA from Vdd1 then the TL431 will only sink 3.7mA.

    Hope this answers the query.

    Regards,
    Pawan