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TPS61193-Q1: Required AC characteristics of Internal switching MOSFET to calculate Maximum Power Dissipation & Boost Output Voltage Formula Clarification.

Bharath Kumar C
Prodigy 40 points
Part Number: TPS61193-Q1
Other Parts Discussed in Thread: TPS61193, LP8867-Q1

We are using the TI TPS61193 LED DRIVER in our design (In Boost Mode), hence we have some below queries & so please clarify it immediately.

 

1)     To calculate Maximum Power dissipation of Device we need to know internal MOSFET AC switching Loss characteristics, this data is not available in datasheet, hence please get this data for us ASAP.

 

2)     We have doubt whether below formula holds good for calculating the boost output Voltage of  VOUT = 42V Max & IOUT = 253mA (Max), VIN = 7.2V (Min) to 15.32V (Max))

 

Let us know like If we use K=0.88 in calculation is that ok. Whether that requires any schematic change.

 

3)     Need to know how below Typical Application Output Voltage is Calculated from above Formula with R1=750K & R2=130K Ohms.

  • 0
    TI__Genius 11836 points

    Hi Bharath,

    1) I am out of office from 10.1 to 10.8 so that the related data can't be sent now.

    2)K = 1 for maximum adaptive boost voltage (typical), K = 0 for minimum adaptive boost voltage (typical), K = 0.88 for initial boost voltage (typical). So you need to check K=0.88,K=0 and K=1 according to the voltage range of LED string.

    3)You can refer to the page 15 of LP8867-Q1 datasheet, it is the same.

  • 0 in reply to Charles-Chen
    TI__Genius 11836 points

    Hi Bharath,

    Do you have any questions about the second and third questions now?

  • 0 in reply to Charles-Chen
    TI__Genius 11836 points

    Hi Bharath,

    I have replied to corresponding FAE through emails since some material can't be provided here. Can we close this thread now?

  • 0 in reply to Charles-Chen
    Prodigy 40 points

    HI Charles,

    Still I don't know like how the Boost Converter output voltage get synched automatically based on the K =0, K=1 & K=0.88 value we select in our calculation to arrive at Specific Boost Output Voltage.

    Second thing is we want know the FET AC Loss which because its significant compare to FET DC Loss, So if we know that data only we can arrive at its Maximum Power Dissipation of Device..

    Please get me the answers above,

  • 0 in reply to Bharath Kumar C
    TI__Genius 11836 points

    Hi Bharath,

    The boost output voltage is controlled by adaptive loop of our device. The three values of K are used to set the output voltage range so that the current sink can output the target current.

    I send a calculation table to FAE through emails and you can refer to it for FET AC Loss calculation.

  • 0 in reply to Charles-Chen
    Prodigy 40 points

    Charles,

    I agree but my question is how K value change will reflect in practical means i.e. in circuit connection or component change anything in hardware,

    For example when we choose Feedback Resistors R1 & R2, IC will read the feedback voltage but in case of K value selection how it reflects to the LED Driver IC is my question actually.

    I did not receive any email about FET AC Loss. 

  • 0 in reply to Bharath Kumar C
    TI__Genius 11836 points

    Hi Bharath,

    The three different values of K just represent three different design conditons, while K = 1 for maximum adaptive boost voltage (typical), K = 0 for minimum adaptive boost voltage (typical), K = 0.88 for initial boost voltage (typical). If you change the value of FB divider, the maximum adaptive boost voltage and minimum adaptive boost voltage will change. So you need to check both K=0 and K=1 according to the voltage range of LED string.  The maximum adaptive boost voltage should be bigger than the maximum voltage of LED string+5V and the minimum adaptive boost voltage should be small than the minimum voltage of LED string. All those design condition has been mentioned in the datasheet of LP8867-Q1, you can refer to it for details.

    You need to email to corresponding FAE to get the calculation table. I just send email to the FAE.

  • 0 in reply to Charles-Chen
    TI__Genius 11836 points

    Hi Bharath,

    Do you have any more questions?

  • 0 in reply to Charles-Chen
    TI__Genius 11836 points

    Hi Bharath,

    I will  close the threads temporarily since I haven't received any reply from you for a time. The thread will be opened again once you ask any questions here.

  • 0 in reply to Charles-Chen
    Prodigy 40 points

    OK, You close this thread.

    Thanks for you're  support.