TPS61085: Can TPS61085 work at the condition that Vin=Vo?

Wayne Wang20

Part Number: TPS61085
Other Parts Discussed in Thread: TPS61230

Hi team,

Customer wants to use TPS61085 to boost the voltage of a super-cap to 5V. The voltage of the super cap is 3~5.5V. Customer has some cercern that if TPS61085 can work at the condition that Vin is very close to Vo.

I use the TPS61085EVM to do the test when Vin=4.8V,Vo=5V. The output voltage ripple becomes much larger than the normal condition. Do you have any advice on why this happen when Vin is close to Vo?

What's more, In our datasheet, it says Vo has to be higher than Vin+0.5. Could you help explain the reason? Thank you.

Best regards,

Wayne

over 7 years ago

0 Helen chen over 7 years ago

TI__Mastermind 40080 points

TPS61085 has minimum Ton limit, so the Vin must lower than the Vo. Suggest you use TPS61230.

0 Wayne Wang20 over 7 years ago in reply to Helen chen

TI__Expert 4380 points

Hi Helen,

I didn't find any information about the Ton limit in our datasheet. How long is the minimum Ton and what's the limit for the duty cycle? Do you have a document that has more detailed information about the TPS61085?

Best regars,
Wayne

0 Helen chen over 7 years ago in reply to Wayne Wang20

TI__Mastermind 40080 points

Yes, datasheet didn't give out the minimum Ton data. But it markes out Vo must 0.5V higher than the Vin. So you must keep this rule.

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TPS61085: Can TPS61085 work at the condition that Vin=Vo?