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TPS65265: question about enable pins

Seokmin Hong
Intellectual 485 points
Part Number: TPS65265

I have some simple questions about TPS65265. This is 3 output Buck Regulator.

I want to control EN1/EN2/EN3 seperatly.

From the datesheet, If i make Mode Pin(#7) floating then, Buck1/2/3 are controlled separate by EN1/2/3.

And in the datasheet, to enable these EN1/2/3, then I should make En1/2/3 pins float because there is internal pullup current source which can make EN pin with floating.

Here, I am confused.

To Control Bucks separately -> Mode Pin Float

To make En1/2/3 Enable -> En1/2/3 Pins are Float.

I want to control En1/2/3 from output logic. But If En1/2/3 pins are floating to enable automatically with internal current source, then How can I control this from outside of IC?

And, one more question.

In the datasheet page 16 there is about UVLO.

Is the Vstart means Uvlo Upper threhsold? and Vstop means UVLO Low threshold?

  • 0
    TI__Expert 7500 points

    Hi Seokmin,

    1. Yes, you can control the EN1/2/3 using outside of IC with the outside IC's output connection with EN1/2/3. When you don't want to enable, making sure the outside IC's output is low. When you want to enable, set the outside IC's is high.

    The EN pin's internal current source can't make the EN high when the EN pin is connecting a low level connection (below the EN threshold voltage).

    2. When EN pin is configured as shown in Figure 26, it can set the customer designed UVLO threshold on PVIN. The Vstart means the PVIN voltage that IC starts to power on (VIN rising). The Vstop means the PVIN voltage that IC shut down (VIN falling).

    Thanks,

    Lishuang

  • 0 in reply to Lishuang Zhao
    Intellectual 485 points

    Thanks for fast reply. 

    Then what happens if i make Enable pin floating? Not high or low?

    In the pin description page 4, 

    Enable for buck1. Float to enable. Can use this pin to adjust the input undervoltage lockout (UVLO) of buck1 3 EN1 with a resistor divider

    And also in the data sheet page 16, there says

    The EN pin has an internal pullup current source, allowing the user to float the EN pin for enabling the device.

  • 0 in reply to Seokmin Hong
    TI__Expert 7500 points

    Hi Seokmin,

    If the EN pin is floating, EN is charged high by the internal pullup current to enable part without external components so as to save PCB area and cost.

    If you want to control the part by outside IC and you should control the outside IC's output high or low to control enable or disable.

    Thanks,

    Lishuang

  • 0 in reply to Lishuang Zhao
    Intellectual 485 points

    Thanks for the reply. This would be very helpful