LP87524B-Q1: Question about switching frequency and phasing

jayk

Part Number: LP87524B-Q1

The datasheet says the part supports Phase Interleaving. Does this mean all four converters are running at the same frequency (in PWM mode) but are shifted 90deg relative to one another? If this is true, what happens when the four output voltages are not all in the same frequency range (as indicated by the fsw spec in the Electrical Characteristics)?

over 7 years ago

0 Karl Wallinger over 7 years ago

TI__Genius 16410 points

Hello Jay,

Yes, it means that all four converters are at the same frequency with 90deg phase shifting.

The fsw spec is showing that the higher frequencies have limited output voltage ranges that they support. At 4MHz, Vout must be greater than 0.8V. If Fsw is set to 4MHz and you set the output voltage of one buck below 0.8V, then the switching clock will change to 3MHz. This will affect the frequency of all converters, since they are synchronized together.

Regards,
Karl

0 jayk over 7 years ago in reply to Karl Wallinger

Prodigy 60 points

Thanks Karl.

Is this true regardless of whether I use the internal RC or an external clock?

How accurate is the internal RC oscillator?

- Jay

0 Karl Wallinger over 7 years ago in reply to jayk

TI__Genius 16410 points

Hi Jay,

The accuracy is in the fsw min and max specified values. It is +/- 10% at each frequency.

I am not sure what happens when using an external clock and you set the voltage lower to a different frequency range. I've copied the device owner on this post to confirm.

Regards,
Karl

0 Tomi Koskela over 7 years ago in reply to jayk

TI__Genius 11020 points

Hello Jay,

Yes this is true with both internal and external clock.

Regards,
Tomi Koskela

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LP87524B-Q1: Question about switching frequency and phasing