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LM34926: Inductor calculation

Brian Wang0928
Genius 14060 points
Part Number: LM34926
Other Parts Discussed in Thread: LM34927

Hello, 

Since supply constrain of the LM34927, customer is estimating if LM34926 with Flybuck can be suited with input/output conditions. could you help to review below design!

CH1：Primary Current

CH2：Primary Voltage

CH3：Secondary Voltage (+5V5)

CH4：Secondary Voltage (+5V6)

questions:

1. In the datasheet, it says the IOUT(Max), is IOUT(max) in peak value or average value? as you can see on the waveform, the peak current is 305mA, it is for the IOUT(MAX)?

2. Follow by the question 1, here is the inductor calculation with 305mA for IOUT(max). and after calculation the inductor value is about 77.5uH. 

Please help to comment. very thanks. 

  • 0
    TI__Guru 72625 points

    Hello

    The best way to check you design is to simulate using the SPICE model 

    on the TI website.

    Thanks

  • 0
    TI__Mastermind 23795 points

    Hi Brian,

    1. Based on the waveforms you've sent, you should be able to use LM34926 as a replacement for this application. The word you are looking for isn't IOUT(max), but current limit. Current limit refers to the output current the device can handle before the device turns the high side FET off. Based on those wave forms, it should be safe to swap to the LM34926 device as the current limit value for the device is 390mA which is more than the 305mA you specified.

    2. The equations you used look solid. 77.5uH should work based on those.

    Thanks,

    Andrew