LM3421-Q1: the variance of continuous conduction switching frequency

Shunsuke Yamamoto

Expert 4946 points

Part Number: LM3421-Q1
Other Parts Discussed in Thread: LM3421

Hi team,

May I know the variance of continuous conduction switching frequency without Rt's variance and Ct's variance?

Best regards,

Shunsuke Yamamoto

10 months ago

0 Xiaoguang1 10 months ago

TI__Genius 14940 points

Hi, Shunsuke,

It depends on application that user is using. For example:

As you can see, for Buck converter, frequency variants with input voltage and output voltage.

Also, reference voltage offset will lead to around +/-5% variance.

Regards

0 Shunsuke Yamamoto 9 months ago in reply to Xiaoguang1

TI__Expert 4946 points

Hi XG-san,

In the case of Boost and Buck-boost mode, what is the variance of continuous conduction switching frequency of IC alone?

Best regards,

Shunsuke Yamamoto

+1 Xiaoguang1 9 months ago in reply to Shunsuke Yamamoto

TI__Genius 14940 points

Hi, Shunsuke-san,

For LM3421 itself, it's like around +/-5% tolerance.

However, you know that the frequency is also affected by RT, CT accuracy.

Furthermore, the formula used below is just simplified to make it easy for calculation. RT/CT charge also related to output voltage, diode and propagation time.

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LM3421-Q1: the variance of continuous conduction switching frequency