TPS61085: TPS61085

Gaurav Kothari

Part Number: TPS61085
Other Parts Discussed in Thread: TPS55340, TPS61087, TPS61175

Hello Sir,

this is Gaurav Kothari from Mumbai, India.

we are manufacturing electronic locks which are completely battery operated (1.5V x 4 AA alkaline duracell battery). now my problem is, in our current design we are using a solonied for locking mechanism. so when the solonied gets active, we get a voltage drop of around 1V, in which sometimes our controller stop responding due to under voltage.

for example, when battery voltage is 5V, and solonied gets active, the voltage drops to 1V and controller stop responding due to under voltage, which is currently 4V. because the controller works at voltage range of 4.5V to 5.5V.

So now we are planning to use TPS61085 where we can get a constant output voltage of 5V whatever the battery voltage may be. so our circuit will be something like battery ---->> TPS61085 circuit ---->> microcontroller circuit.

so if i add TPS61085 in series between my battery and microcontroller circuit, will it keep the controller voltage constant at 5V even if the solonied gets active. The current consumption is approx 2 Amps.

over 6 years ago

0 Helen chen over 6 years ago

TI__Mastermind 40080 points

Hi Sir,

If you use TPS61085, make sure Vo is at least 0.5V higher than the Vin because of the minimum Ton requirement. What is your input voltage range in this application?

0 Gaurav Kothari over 6 years ago in reply to Helen chen

Intellectual 330 points

My source voltage is from 1.5V x. 4 AA alkaline battery, which is from approx 6.4V to 3V

0 Helen chen over 6 years ago in reply to Gaurav Kothari

TI__Mastermind 40080 points

Hi sir,

So Vin is >vo, so TPS61085 is not fit if you need a 5V fixed output voltage. You need to use a buck-boost conveter or sepic converter to realize the function.

0 Gaurav Kothari over 6 years ago in reply to Helen chen

Intellectual 330 points

Can you suggest me any IC for the same for ateast 2 amps load

0 Helen chen over 6 years ago in reply to Gaurav Kothari

TI__Mastermind 40080 points

Hi Sir,

Suggest you use TPS55340 in sepic topology.

0 Gaurav Kothari over 6 years ago in reply to Helen chen

Intellectual 330 points

Thanks,,

We have gone through the specification and design of this IC. The cost of this IC is quite high and even the output current rating is approx 4A. we initially had a load current of 2.5A, so in that case this IC was suitable for our design. But again we tried reducing the power consumption of or circuit. so we hardly need 800mA of current. so in that case this using this IC is not reliable. can you please suggest me any IC which can support approx 1A of load current.

0 Helen chen over 6 years ago in reply to Gaurav Kothari

TI__Mastermind 40080 points

Hi Sir,

You need to know what is the load current. If you can make sure the load current is lower than 1A, then TPS61085 is still fit. But if the load current is higher than 2A, then you have to use TPS61087 or TPS55340. And you should choose a Sepic topology instead of the Boost topology.

0 Gaurav Kothari over 6 years ago in reply to Helen chen

Intellectual 330 points

Thanks,

But initially you told me that, in the case of TPS61085, If you use TPS61085, make sure Vo is at least 0.5V higher than the Vin because of the minimum Ton requirement.

As i am powering the system with 3V to 6V variable power supply using 4 x AA batteries. and i need a Vo=5V fixed.

0 Helen chen over 6 years ago in reply to Gaurav Kothari

TI__Mastermind 40080 points

Hi Sir,

Very good question. You need to use Sepic topology instead of the Boost topology. For the Sepic, then Vin can be higher or lower than Vin.

0 Gaurav Kothari over 6 years ago in reply to Helen chen

Intellectual 330 points

so, can you please recommened me some IC's for sepic topology.
i maximum load current is 1 Amps.

0 Helen chen over 6 years ago in reply to Gaurav Kothari

TI__Mastermind 40080 points

TPS61175 SEPIC Design.pdfHi Sir,

please check the attached design sheet. it use TPS61175, but also fit for the TPS61085/TPS61087. The concept is the same.

0 Gaurav Kothari over 6 years ago in reply to Helen chen

Intellectual 330 points

Thanks,

I think this IC might solve our problem. But gone through the datasheet, but couldn't find any application circuit for sepic topology. Do you have any.

0 Helen chen over 6 years ago in reply to Gaurav Kothari

TI__Mastermind 40080 points

Hi Sir,

We don't have either. We only have TPS61175 in sepic schematic. We can draw the schematic for your. But you need to build a board to double check it.

0 Gaurav Kothari over 6 years ago in reply to Helen chen

Intellectual 330 points

Yes...

Please provide me the circuit diagram for sepic topology for TPS61175 IC. I will design the PCB and test it on our side.

Please make sure the circuit works for Vin from range 3V to 6.5V and Vout = fixed 5V. Also please provide the maximum current for the same.

0 Helen chen over 6 years ago in reply to Gaurav Kothari

TI__Mastermind 40080 points

Hi Gaurav,

I'll send the schematic to you within two days. Are you sure you want to use TPS61175?

0 Gaurav Kothari over 6 years ago in reply to Helen chen

Intellectual 330 points

Yes, am sure, we will go with TPS61175 IC.

0 Helen chen over 6 years ago in reply to Gaurav Kothari

TI__Mastermind 40080 points

Hi Sir,

Per calculation, I found TPS61175's peak switch current is not enough for the application. In this application, the peak switch current will be as high as 5.3A with a 3.3uH coupled inductor. So suggest you choose TPS55340. the cost of TPS55340 is nearly the same with TPS61175.

0 Helen chen over 6 years ago in reply to Gaurav Kothari

TI__Mastermind 40080 points

Please close the post and open a new post with the right part number if you have some other questions.

0 Gaurav Kothari over 6 years ago in reply to Helen chen

Intellectual 330 points

The peak current of TPS61175 is around 3 Amps which is more than enough for me for our application. Our maximum current dissipation is not more than 2 Amps

0 Helen chen over 6 years ago in reply to Gaurav Kothari

TI__Mastermind 40080 points

Hi Sir,

Your output current is 2A. which mean the peak inductor current is higher than 2A.

For the sepic converter, the peak switch current is IL1+IL2, so the peak switch current is higher than 5A considering the conversion efficiency. You need to choose the IC according to the peak switch current.

0 Gaurav Kothari over 6 years ago in reply to Helen chen

Intellectual 330 points

Sorry..

But did not get your point, what IC should i use. what IC do you recommened.

0 Helen chen over 6 years ago in reply to Gaurav Kothari

TI__Mastermind 40080 points

Hi Sir,

Please choose TPS55340.

0 Gaurav Kothari over 6 years ago in reply to Helen chen

Intellectual 330 points

Thanks...

we will surely use TPS55340. I will initially prepare a circuit diagram as per the drawings you sent me, and will forward it to you, request you to please go through it and let me know it the circuit diagram is correct.

0 Gaurav Kothari over 6 years ago in reply to Helen chen

Intellectual 330 points

Sepic Converter.PDF

0 Gaurav Kothari over 6 years ago in reply to Gaurav Kothari

Intellectual 330 points

This is a circuit diagram of TPS55340. please check ad let me know if the things are fine

0 Gaurav Kothari over 6 years ago in reply to Gaurav Kothari

Intellectual 330 points

You did not mention the value of R2

0 Helen chen over 6 years ago in reply to Gaurav Kothari

TI__Mastermind 40080 points

R2 can be 28.7k . Please open a new post if you have other questions about TPS55340. Let's close this post since the topic is TPS61085, this will confuse the other customers.

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TPS61085: TPS61085