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TPS22930A: inrush current issue

Yue TANG
Expert 8705 points
Part Number: TPS22930A
Other Parts Discussed in Thread: TPS22918

Hi, 

TPS22930A shows that it supports controlled inrush current. but can't find the description from datasheet.  please kindly suggest how to control the inrush current. My customer has used  TPS22930A in their design, but the Cin and CL show that there is  a high risk to meet inrush current. please suggest how to improve it or  recommend  a better device for this case, thanks.

CIN：10UF/0603+100NF/0402

CL： 470UF/7343+10UF x2/0603+100nf x10/0402

 

  • 0
    TI__Mastermind 32650 points

    Hi Yue,

    For this device, the inrush current is mitigated internally by changes in the slew rate. There is no external control on this power switch that changes the slew rate.

    Depending on the application/use case, the customer could reduce inrush current as easily as adding a resistor yet such a method could be lossy/non-ideal.

    What was the deciding factor for the customer to choose the TPS22930A? I do not want to recommend a switch that wont work with the customer's concerns. For example, if the customer cares about having a 4 pad device, then the TPS22918 will not work even though it has user controlled slew rate capabilities.

  • 0 in reply to Shreyas Dmello
    TI__Expert 8705 points

    Shreyas,

    Their main concern is the input voltage drop due to  the big  capacitive load at the output side. actually, they don't want to change the design. just want to know if there are some potential risks.  According to the datasheet, A CIN to CL ratio of 100 to 1 is recommended for minimizing VIN dip caused by inrush currents during startup, But in my customer case,  it was the reverse, CL is about 50 times bigger than CIN.

    Is there a description or diagram  to show the  the inrush current mitigation as you mentioned  in datasheet? would like to know more about this feature to better explain to my customer. 

  • 0 in reply to Yue TANG
    TI__Mastermind 32650 points

    Hi Yue,

    As far as the TPS22930A is concerned, the slew rate characteristics are described in a little more detail in section 7.6 and with waveforms in section 7.7.1 of the datasheet.

    We ask for a input capacitance mainly to maintain the supply voltage and protect the supply not necessarily the part itself. The input to load capacitance ratio of 100 to 1 is only recommended when driving large capacitive loads so as to mitigate any reverse current through the body diode and to protect the supply. In most cases this is not required. I think that in your customer's use case, there shouldn't be an issue. 

    I just want to reiterate that this device has no user slew rate control.