LP8732-Q1: minimum ON time

nnn sato

Prodigy 230 points

Part Number: LP8732-Q1
Other Parts Discussed in Thread: PEET-GUI

Tool/software:

I would like to know the minimum ON time(typ and max) for the step-down DCDC.

over 1 year ago

0 Field Tolson over 1 year ago

TI__Genius 10772 points

Hi Sato,

Typical rise/fall time of is around 1.5ns, but please note that it also depends on the PCB parasitics of the SW-node, but this is a typical value.

For efficiency calculations you can use our tool: https://www.ti.com/tool/PEET-GUI.

Thanks,
Field

0 nnn sato over 1 year ago in reply to Field Tolson

Prodigy 230 points

Could you also tell me the minimum off time (type and maximum) of the step-down DC-DC?

I would like to use formulas 12 and 13 from Application Report "SLVA477B" (Basic Calculation of a BuckConverter's PowerStage), but are the ripples in these formulas peak-to-peak values?

0 nnn sato over 1 year ago in reply to Field Tolson

Prodigy 230 points

The typical rise/fall time of 1.5ns seems quite fast, but will it really work at this value?

0 Field Tolson over 1 year ago in reply to nnn sato

TI__Genius 10772 points

Hi Sato,

nnn sato said:
formulas 12 and 13

In section 8.2.1.3 on page 64 of the datasheet linked here, has the recommended output capacitance values. You can search online to find values of ESR for capacitors as desired. We also have a PSpice model available on TI.com to test for selected values or designs. But using the PEET-GUI above, you should be able to find the efficiency as desired and calculate from there. Or you can select a capacitance value or multiples of these and rearrange the equation to solve for your desired variable.

Thanks,
Field

0 nnn sato over 1 year ago in reply to Field Tolson

Prodigy 230 points

Could you please tell me the details of the minimum ON time?
Is it "rise time + ON period + fall time"?
Is the minimum ON period 0ns?

I would like to know how to think about it.

0 nnn sato over 1 year ago in reply to nnn sato

Prodigy 230 points

Could you please reply to the above questions?

0 Field Tolson over 1 year ago in reply to nnn sato

TI__Genius 10772 points

Hi Sato,

Due to the holiday in the US today, I will hope to get you information tomorrow or early next week since most of the experts are currently out of office.

Thanks,
Field

0 nnn sato over 1 year ago in reply to Field Tolson

Prodigy 230 points

Could you please reply to the above questions?

+1 Matt Sunna over 1 year ago in reply to nnn sato

TI__Guru* 81034 points

Hi Sato,

I do not have this information available from our documentation. Can you use the Pspice model from the product folder (https://www.ti.com/product/LP8732-Q1#design-tools-simulation ) to get what you need?

Regards,

Matt

Power management

Power management forum

LP8732-Q1: minimum ON time