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L7987 switching frequency

PZha.1
Associate III

HI Sir,

how do we define the switching frequency of the L7987

the switching frequency range is between 250KHz and 1.5MHz

looks like if the switching frequency is set to 1.5MHz, the ripple appears to be much smaller, 

so can we set it to 1.5MHz under normal design.

thanks,

With best regards,

PZha

 

1 ACCEPTED SOLUTION

Accepted Solutions

Hi,

>is there any difference if the switching frequency is set to 10K 1.5MHz and NC 250KHz

hmm... the switching frequency is about (with 10K )  1.5MHz and NC is  250KHz .

Your circuit (the coil L1 , C5+6) has to match the frequency you want/set .

What else ...?

If you feel a post has answered your question, please click "Accept as Solution".

View solution in original post

4 REPLIES 4
AScha.3
Chief

Hi,

see ds :

AScha3_0-1716216846547.png

setting Rfsw to 10k should give about 1.5M.

here R8 :

AScha3_0-1716217001609.png

 

If you feel a post has answered your question, please click "Accept as Solution".
PZha.1
Associate III

HI Sir,

thanks for your reply, 

could you please advise is there any difference if the switching frequency is set to 10K 1.5MHz and NC 250KHz

thanks, with best regards, PZha

 

Hi,

>is there any difference if the switching frequency is set to 10K 1.5MHz and NC 250KHz

hmm... the switching frequency is about (with 10K )  1.5MHz and NC is  250KHz .

Your circuit (the coil L1 , C5+6) has to match the frequency you want/set .

What else ...?

If you feel a post has answered your question, please click "Accept as Solution".

HI Sir,

thanks for your support.

with best regards, PZha