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TPS7B7702-Q1 Maximum Current Limit

Joe Howard
Intellectual 2970 points
Other Parts Discussed in Thread: TPS7B7702-Q1, TPS7B7702

I was wondering if it's possible,using the TPS7B7702-Q1, to short the LIMx pins to GND and tie the OUTx pins together in order to achieve a higher output current closer to 500mA (550mA is the internal limit)?

Cheers,

Joe Howard

  • 0
    TI__Mastermind 20590 points
    Hi Joe, the appropriate engineer has been assigned to this post. Best Regards, Scott
  • 0
    TI__Expert 5675 points
    Hi Joe,

    We have already discussed this through email communication. Thanks!

    Best regards,
    Jason Liu
  • 0 in reply to Jason. Liu
    TI__Intellectual 2970 points
    Can you please answer this here for anyone else that would have the same question? E2E is supposed to be a knowledge base for all to use.

    Also, you never answered this part of my question in the email.
  • 0
    TI__Expert 5675 points
    Hi Joe,

    Sure. For this antenna LDO, there are two methods to set the current limit value, one is set by the external resistor and another is use the internal current limit value by connect the LIMx pin to GND.

    With external current limit resistor, users could get a very accurate current limit value with only 8% tolerance.
    In the other hand, the tolerance of internal current limit value would vary from 340mA to 550mA. However, this is already much more accurate than most of the LDO products with internal current limit in the market.

    Therefore, we do not suggest user to use this antenna LDO with more than 300mA current limit.

    Also, as explained in the email, dropout voltage would be higher when use with high current >300mA. In theory, worst case would be more than 2V voltage drop under 500mA conditions.

    Best regards,
    Jason
  • 0 in reply to Jason. Liu
    TI__Guru** 103215 points

    Hello Jason,

    I'm wondering if it would be possible to share current between the two outputs of the TPS7B7702 to allow for one single output at 500mA. We have an app note on LDO current sharing using ballast resistors:

    Given the tolerance of the device regulation, my calculations led me to pretty sizable resistors (around 3 ohms) in series with the outputs, which would certainly cause a large voltage drop at the output at 500mA.

    Another scheme I saw utilized a current sensing mechanism to control the feedback of one of the outputs in order to balance currents without the need for ballast resistors: '

    In this case, a difference amplifier was implemented with the current input (or output) being sensed at both LDOs. Would it be possible to implement a scheme like this by utilizing the built-in current sensing feature of the TPS7B7702? 

    Thanks,

    Casey