LP87524B-Q1: Recommended L value

Kazuhiko Hirano

Genius 11613 points

Part Number: LP87524B-Q1

Hello,

My customer plans to use LP87524B with switching frequency = 10MHz or 20MHz.

Their requirements are as follows.

VIN_B0, VIN_B1, VIN_B2, VIN_B3, VANA = 3.3V

Buck0 = Unused

Buck1 = Unused

Buck2 = 0.9V/2A, ripple voltage <2mV (or <1mV if possible)

Buck3 = 0.9V/2A, ripple voltage <2mV (or <1mV if possible)

They do not know how to select proper L value for fsw=10MHz and 20MHz cases.

Could you provide recommended L value for both cases, please?

Best regards,

K.Hirano

over 4 years ago

0 Kazuhiko Hirano over 4 years ago

TI__Genius 11613 points

Hello,

The customer would also like to know recommended Cout value for Fsw=10MHz and 20MHz cases.

Best regards,

K.Hirano

0 Layne J over 4 years ago in reply to Kazuhiko Hirano

TI__Genius 12735 points

Hi Hirano-san,

LP87524B operates between 2.2 MHz and 4.4 MHz according to the datasheet. Can you verify this is the correct part number? I have also forwarded this thread to the expert for this part.

Best regards,

Layne J

0 Kazuhiko Hirano over 4 years ago in reply to Layne J

TI__Genius 11613 points

Layne J,

The datasheet says “The LP87524B/J/P-Q1 also supports switching clock synchronization to an external clock. The nominal frequency of the external clock can be from 1 MHz to 24 MHz with 1-MHz steps.” My customer thought this means that Fsw could be set 1MHz to 24MHz with 1-MHz step. But their understanding is wrong?

Best regards,

K.Hirano

0 Layne J over 4 years ago in reply to Kazuhiko Hirano

TI__Genius 12735 points

Hi Hirano-san,

Thank you for point that out. You are likely correct about the external clock but I will let the expert for this part comment further.

Best regards,

Layne J

0 Jari Niemela13 over 4 years ago in reply to Layne J

TI__Expert 5600 points

Hi Hirano-san,

External clock sync is divided to switching clock level based on what is selected on EXT_CLK_FREQ bits. So if user inputs 20MHz (range -30 - +10%) to CLKIN-pin and PLL_MODE bit is set enabled and EXT_CLK_FREQ bits matches to 20MHz CLKIN clock is then phase locked to external clock but switching frequency is still 4MHz.

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LP87524B-Q1: Recommended L value