TPS55065-Q1: Problem with startup volatge

Hi Alone

The buck-boost converter of this high input voltage normally need 5V from input side or output side to supply internal circuit. so we don't have a device to startup from 2V. but the device can operates down t 2V after finish start up. May I know why you need this low startup input voltage?

About the 5.8V issue, I need to check with the EVM and come back this week or early next week.

Hello Jasper Li
Thanks for your feedback.
Yes, I known this, but my issue when input voltage below 5.8V before startup process finished.
Really in my project need 5-5.8 V supply for circuit from 2-26V input voltage from solar.
I checked and dont have boots converter (SEPIC) support that.
Can you re-check and suggest for me if input voltage change to 2-18V input supply?
Thanks.

Hello Jasper Li
Does have any update from you?
Thanks.

Hi Alone,

Even for the 2-18V input voltage range, We don't have a solution to get 5~5.8V output (considering both startup and stable operation). The device has the ability to startup from 2V can't support 18V input voltage. The device can support 18V input voltage can't startup from 2V.

the closed solution is a boost converter TPS61175 to generate >10V output, then a buck converter to 5V output.

Hello Jasper Li
Yes, I agree with you, im also checked but can not find any IC suitable.
But your solutions is not good when boots upper than 10V and use buck converter after that.
Because the input voltage can reduce lower ( about 3V) so boosting to 10V is'nt a good solution for me.

So I must change input voltage from 3.3V to 24V. and we're intend to use with LM3488.
Really, in my system get power from solar panel ( 1.8-28V) and charging for 1 cell battery (4.2V) via buck. boost converter.
If you known an IC can intergrated my requirement, pls help me.
Thanks you.

Hi Jasper Li
Many thanks for your suggestion.
But Im afraid that we missed understood together about my purpose.

My system power similar as:

Solar Panel (3-26V) -> High voltage Protection Block( 3-26V) -> Buck/ Boost Converter(5v) -> Battery charger -> Battery (4.2V max)

So, i odnt understand about " Use a TPS55340, power its VIN pin with the battery voltage. as VIN voltage is higher than 3V, the boost converter keeps switching even the power input is only 1.8V."
Because battery only connect after battery charger.
Please check and confirm.
Thanks

Hi NTC
In this sentence " Use a TPS55340, power its VIN pin with the battery voltage. as VIN voltage is higher than 3V, the boost converter keeps switching even the power input is only 1.8V."
the power input is the solar panel, which is 2~26 (it seem you can increase the minimum voltage to 3V). The power input is connected to the power inductor in a boost converter. The VIN pin is not the power input. the VIN pin can be powered by other voltage source. for the TPS55340, the minimum voltage of the VIN pin is 2.9V. the current requirement into this VIN pin is small. that is why we can use the battery to power this pin. please refer to this application note "www.ti.com/.../slyt556.pdf"

As the minimum voltage is 3V, we can directly use the TPS55340 + a buck or the SEPIC circuit based on TPS55340.

Hi Jasper Li

Thannks for your fast feedback.

Im sorry about my wrong understand about your idea.

Really i need solve this issue asap to rework on my project.

As your suggestion, Im only affraid when battery charge will have more phase of charge.

Will this affect on VIn pin of TPS55340 ?

My final purpose is only need charge for battery and generating 3.3v and 5V for supply of another sensor on board.

So, Im searching a battery charge support wide vin range ( 3-26V) and intergrated LDO or SW power that have ability to generate 5V/3V3.

Thanks.

Hi Jasper Li
Do you have any suggest?
Thanks

Hi NTC,

your drawing is really the image I were think. this circuit will work if the battery voltage no lower than 3V. you can also change the circuit to SEPIC to avoid using a BUCK. there is a SEPIC EVM based on TPS55340 for your reference.

if you need to generate a 5V from a battery, I would suggest TPS61230A. depending on output current requirement. The 3.3V output can be from a LDO

I know nothing about battery charger. I would suggest you start another post with title of change requirement. other expert will help to support Charger.