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LM5116: VCCX and DEMB pin description

Skylar Li
Intellectual 1980 points
Part Number: LM5116

Hi experts,

    Here are two questions.

1. The pin description of VCCx is different from the block diagram.

2. Could you pls help explain DEMB function? Thanks.

BR,

Skylar

  • 0
    TI__Guru 58761 points

    Hello Skylar

    1. Would you please tell us the difference you are thinking about ? 

    2. Diode emulation mode control pin . The inductor current is sensed by monitoring the voltage between SW and DEMB. As the SS capacitor continues to charge beyond 1.215 V to 3 V, the DEMB bias current will increase from 0 µA up to 40 µA. With the use of an external DEMB resistor (RDEMB), the current sense threshold for diode emulation will increase resulting in the gradual transition to synchronous operation. 

    -EL

  • 0 in reply to EricLee
    TI__Intellectual 1980 points

    Hi Eric,

        From the block diagram, it means if VCCX< 4.5V, the mosfet will turn on and then VCCX is internally connected to VCC. But the pin description is different. Could you pls help it? Thanks.

    BR,

    Skylar

  • 0 in reply to Skylar Li
    TI__Guru 58761 points

    Hello Skylar

    P-Channel MOSFET turns on when the gate is pulled down. Which means the switch connecting VCCX to VCC will turn on when the 4.5V comparator output is in low logic state.

    -EL