TPS61178: External clocking at light loads

John Griffith

Part Number: TPS61178

Hello,

For my customer, being able to externally clock all the switching converters is a must since they time teh switching off cycle with their acquisitions. They are concerned that at light loads the TPS61178 might change its switching frequency. The datasheet says:

At the light load, the TPS61178 enters into the auto PFM mode while TPS611781 is in the forced PWM mode.

Does that mean that they should look at the TPS611781 and externally clock it? Their use case is 5.8V in and typical ~20mA load, but spikes up to 100-150mA.

Thanks,

John

6 months ago

0 Fergus He 6 months ago

TI__Genius 11555 points

Hi John,

Yes, TPS611781 needs to be used to synchronized to external Clock.

Could you tell me the output voltage? it seems that TP61178's current limit will be over spec.

Regards,

Fergus

0 John Griffith 6 months ago in reply to Fergus He

TI__Mastermind 21491 points

Hi Fergus,

Thanks for the quick response! I forgot to add that, the output voltage is 19V, VIN 5.8V (regulated output), and 20mA out typical and 100-150mA peaks.

Thanks,

John

0 Fergus He 6 months ago in reply to John Griffith

TI__Genius 11555 points

Hi John,

It seems that TPS611781 is the most suitable device with 19V output and sync function.

Please connect me if there is any other question.

Regards,

Fergus

0 John Griffith 6 months ago in reply to Fergus He

TI__Mastermind 21491 points

Okay, so the TPS611781 will not do any pulse skipping, it does the forced PWM? And the TPS61178 does the PFM mode? Correct?

Thanks,

John

+1 Fergus He 6 months ago in reply to John Griffith

TI__Genius 11555 points

Hi John,

Yes, TPS611781 is FPWM mode at light load, while TPS61178 is PFM at light load.

Regards,

Fergus

0 John Griffith 6 months ago in reply to Fergus He

TI__Mastermind 21491 points

Thanks!

John

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TPS61178: External clocking at light loads