LM3478: LM3478

Hello Haruo,

The datasheet gives some typical characteristic graphs for 100kHz, so you can use it at this frequency, it is not very often used at such a low frequency. What is the reason that you want to go such low?

Hello Brigitte,

In the datasheet, Fnom is specified min 350kHz, Max 440kHz for typ 400kHz with RFA = 40kohm over temperature.

In case of typ 100kHz, customer can think Fnom has same variation as well as in case of typ 400kHz ?

Customer worried about entering unstable operation or getting large variation of SW frequency by using 100kHz SW frequency.

Since the RFA has also variation, if SW frequency was configured 98kHz by the resistor variation, LM3478 wouldn’t work...

The above case might be happened ?

Thank you and best regards,

Michiaki

Hi Michiaki,

Your analysis here is basically right. As the variation at 100kHz is not given in the datasheet, please leave enough margin when selecting the RFA so that the actual operation frequency is >=100kHz. Otherwise, the performance will not be guaranteed.

Thanks,

Yinsong

Hello Yinsong,

Customer will have some margin to meet datasheet spec but they are wondering how much variation for SW frequency they should estimate.

For instance, if they configure SW frequency at 110kHz with margin, how much variation does LM3478 have ?

Customer can use same ratio for the variation, showing 350kHz – 440kHz variation for 400kHz in the datasheet ?

Thank you and best regards,

Michiaki

Hi Michiaki,

I have asked our designer about this. Let's wait for their feedback.

Thanks,

Yinsong

Hi Michiaki,

Sorry but we don't have more information here. The only reference would be the figure 5 curve in the datasheet, which shows a very small variation.

Thanks,

Yinsong