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LMR14020-Q1: LMR14020

Maris Prasath C M
Prodigy 60 points
Part Number: LMR14020-Q1
Other Parts Discussed in Thread: LMR14020, LMR14050

Hi,

      I am using LMR14020 (HSOIC package) Automotive qualified  component for one of my Project.The following Inputs are Vin=6V to 16V ; Vout= 5V; Fsw=2.1 MHz. The schematics as shown below

When I apply Input voltage=6V . The voltage across buck input pin is 5.18V for 0.5A Load rate & 5.03V for 1A  and also the output voltage is 4.866V (0.5A) & 4.585V (1A). The switching frequency at input voltage = 6V is given below

The switching frequency goes to 200 KHz .Instead of 2.1MHz (which is  I'm using). Is it the switching frequency really decreases based on the input? Are there is any error due to internal compensation circuit.

And I also having problem in transient stability at 6V and I also can't get desired frequency (1/20 Fsw< Fc<1/10 Fsw). The bode plot is attached below. Kindly clarify whether it operates under Input voltage =6V. If yes what about its switching frequency and its transient stability?

  • 0
    TI__Mastermind 27470 points

    HI 

    LMR14050 has dropout feature which will make Toff constant and decrease the frequency and extend its duty cycle. 

    when it come to dropout condition, it is no more PCM mode.if you want to get desired the bode plot, you need let the chip work at 2.1Mhz frequency which means you have to raise up you input voltage.