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Use LT3010 to power LTC4020 INT_Vcc

hello

I see in the datasheet that the LT3010 is used to power INT_vcc. May I ask whether the GND of LT3010 is connected to SGND or PGND

BI1IZF

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  • I am glad you asked this question because the use of the INTVcc preregulator in datasheet figure 9, figure 10 and the application circuit on p. 39. will not work.  Please use the following circuit instead.  Note that I have connected the ground pin of the LT3012 to PGND. 

    I used the LT3012 which can supply 250mA; the LT3010 can supply 50mA.

  • Hello.

    To be honest, I'm a little confused. What is the reason why the circuit will not work in datasheet on p. 39? Because a low power regulator (LT3010) is used? Or is it not the correct wiring diagram? As I can see from your figure, you connected the regulator output to the PVIN and INT_Vcc pin of LTC4020. But, according to the block diagram on page 14 of the datasheet, pin PVIN  is an input, and INT_Vcc is an output. And in your circuit they are shorted. It is correct?

    After reading a few more topics on the forum, I found the following recommendation for connecting an regulator .  

    Recomendation from ADIApproved

    As we can see from the figure, the regulator is connected only to the PVIN pin. And the INT_Vcc pin is connected only to the anodes of the diodes that power the transistor driver.  This connection allowed the internal INT_Vcc regulator to do its work with a lower input voltage. But still maximum current is limited by 150 mA value.

    If connect the transistor drivers (BST1, BST2) not to the INT_Vcc pin (via diodes), but directly to the LT3012 (shown in the figure)? Will this be correct? In this case, there will be no short circuit between the INT_Vcc pin and PVIN of LTC4020 , and the entire power load for the transistor drivers is completely loaded on the LT3012.

    Sorry for my english, best regards.

Reply
  • Hello.

    To be honest, I'm a little confused. What is the reason why the circuit will not work in datasheet on p. 39? Because a low power regulator (LT3010) is used? Or is it not the correct wiring diagram? As I can see from your figure, you connected the regulator output to the PVIN and INT_Vcc pin of LTC4020. But, according to the block diagram on page 14 of the datasheet, pin PVIN  is an input, and INT_Vcc is an output. And in your circuit they are shorted. It is correct?

    After reading a few more topics on the forum, I found the following recommendation for connecting an regulator .  

    Recomendation from ADIApproved

    As we can see from the figure, the regulator is connected only to the PVIN pin. And the INT_Vcc pin is connected only to the anodes of the diodes that power the transistor driver.  This connection allowed the internal INT_Vcc regulator to do its work with a lower input voltage. But still maximum current is limited by 150 mA value.

    If connect the transistor drivers (BST1, BST2) not to the INT_Vcc pin (via diodes), but directly to the LT3012 (shown in the figure)? Will this be correct? In this case, there will be no short circuit between the INT_Vcc pin and PVIN of LTC4020 , and the entire power load for the transistor drivers is completely loaded on the LT3012.

    Sorry for my english, best regards.

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