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LV14360: Max duty at fsw=600kHz

Jade Han
Intellectual 1575 points
Part Number: LV14360

Tool/software:

Hello experts,

I hope to find what the minimum Vin LV14360 can intake for load of Vout=24Vin & Iout=1A (max).

On datasheet it says max duty is 90% with fsw=200kHz, but I assume at 600kHz, max duty would be different.

I couldn't find any info/graph on max duty at fsw=600kHz, or min on-time, etc..could I ask what it would be?

In summary I have 2 questions,

1. What is max duty cycle at 600kHz?

2. What is the frequency that can support maximum max duty possible? (ex. If fsw=100kHz can support even larger max duty, please let me know.)

Thank you in advance for your support.

  • 0
    TI__Expert 5490 points
    1. The 90% duty cycle limitation comes from the boot capacitor recharge circuit. When operating with a low voltage difference from input to output, the high-side MOSFET of the LV14360 operates at approximate 90% duty cycle to recharge the BST capacitor. And it is independent of the switching frequency selected through RT resistor.  This behavior is explained in “8.3.4 Low Dropout Operation and Bootstrap Voltage (BOOT)” section of the datasheet.
    2. As explained above, the max. duty cycle doesn’t change w.r.t switching frequency. What is the input voltage, output voltage and output current customer is looking? Let me know if you need further help.
  • 0 in reply to Nityanand Hegde
    TI__Intellectual 1575 points

    Hi Nityanand,

    Thank you so much for your detailed feedback! I understand much better now.

    Customer wants to design with 25Vin 24Vout 1Aout(max), and it seems with max duty of 90%, min Vin should be 26.67V, however Webench simulation creates results for 25~27Vin 24Vout 1Aout(max). (Please find the Webench sim result pdf file below.)

    Would it be possible for customer to design with 25~27Vin? What is the minimum Vin customer can design with?

    WBDesign_LV14360_minVin.pdf

    Thank you for your support.

    Best regards,
    Jade

  • +1 in reply to Jade Han
    TI__Expert 5490 points

    Hi Jade,

    Let's follow-up on the email. 

    Thanks,

    Nitya