tps63060

TPS63060 has a dynamic current limit. Please see Fig. 7 in the datasheet.
Are you operating the device in different VIN/VOUT conditions where the current limit value is different?

I've removed your second post to keep one discussion:
---------------------

Hi Florian,



Florian Feckl replied to tps63060.

TPS63060 has a dynamic current limit. Please see Fig. 7 in the datasheet.
Are you operating the device in different VIN/VOUT conditions where the current limit value is different?



In my application Vout is fixed at 7.1V and the input range (battery) is between 4 and 6 volts.

I want that current limit is near 1.8A in the operation range.

Sorry but i do not understand the need of Fig7 in my application. Can you explain me?



Thank you,

Christophe

I understood that in you are charging a super-cap in your application. This means that the output voltage is less than the target voltage. The device tries to bring up the output voltage and is not able as it limits the current itself. This would mean i takes time until the super-cap is charged...
The current limit cannot be programmed by the user. It is internally defined as shown in the curve.

Basically: Is it correct that your goal is to charge a super cap to maximum 7.1V with 1.8A typical?

I've removed your third post to keep one discussion, please stick to this thread;
---------------------

Florian Feckl replied to tps63060.

I understood that in you are charging a super-cap in your application. This means that the output voltage is less than the target voltage. The device tries to bring up the output voltage and is not able as it limits the current itself. This would mean i takes time until the super-cap is charged...
The current limit cannot be programmed by the user. It is internally defined as shown in the curve.

Basically: Is it correct that your goal is to charge a super cap to maximum 7.1V with 1.8A typical?

Hi Florian,

exactly , my goal is to charge a super cap at about 7.1V with a limit of current (to avoid inrush current)

1.8A is the max value I have seen when charging capacitor ith EVM-619.

the target is to divide the pulse current between super cap and battery during the life time.

Christophe

TPS63060 is designed to regulate to a specific output voltage, not a specific input current. The max input current is determined by the internal limit value. This is dynamically and represented in Figure 7 (Figure 7 shows the current limit in general, which is input Clim for boost and output CLim for buck mode).
To regulate to a specific input current, you can think of an application circuit that measures the input current and influences the feedback node as an outer regulation loop.

Hi Florian,

According to figure7 it should limit to about 2A but this is not what we see.

On the demo board, we see that on pin 1 there is a 2.4MHz signal with 64-66% duty cycle, and on pin 10 we see ~85% duty.  However on our board there is no modulation on pin1 (because the IC does not limit the current and so keeps drawing from the supply??) and only occasional pulses on pin 10.  Do you know why please?

Has the device changed at all in the last 6 months? The datasheet seems to have had a revision?

Christophe

Sorry, the information above is wrong: On the demo board the pin 1 frequency is ~2.4 MHz with 64-66% duty cycle and pin 10 is ~85% duty cycle with and without a load. On our board pin 1 is not switching normally (only occasional switches) and pin 10 is varying between 2.4 -2.5 MHz, 83% duty cycle with no load and varying between 2-3 MHz, 65-76% duty with a load.

Christophe

Some new information:

We have two demo boards that behave the same (and as required). We have now swapped one of the demo board ICs for one of the ICs on our board and the behaviour follows the IC. So can you tell us if there has been any changes to the IC please?

No, there where no changes to the silicon. The revision was according to several documentation sections. Please see chapter 4 for detailed info's.
The different behaviors of the two switch nodes are related to a different operation point of the device. When VIN/VOUT and load are not exactly the same, the behavior will be significantly different. That is the nature of a DC/DC Converter...
Please make sure that the conditions are exactly the same, like when the cap is empty or fully charged.
To do equivalent test for the current limit, you can short circuit the output (which represents an empty cap) and evaluate the input current.

so you are shorting the output in both cases and do not see a higher current than 140mA?
Can you describe your setup and share your results?

Hi Florian,
Setup is as followed:

I use a TPS63060_EVM_619
I do a short circuit with a strap between Vout and Gnd
Switch PSU on
Measure PSU supply with current probe .

Result is that the current is not higher than 140mA.

Maybe can you realise the same test than me?
Christophe

Hi Christophe,

I will jump in since Florian is ooo.

The TPS63060 operates with a lower current limit as long as the output voltage is below 1.2V (see Chapter 8.3.2).
This is probably what you see when shorting the output.

Could you please share your schematic and layout? What are the differences between TI EVM and your circuit?

In general you would need a boost converter with a current limit. Is this correct?

Regards,
Michael

Hi Michael

Let me first explain my design.
We need to supply an handheld transmitter with battery with a range between 6V (fresh battery) to 3.5V (end of life).
The use of boost converter is to fix the working voltage at 7.5V for RF amplifier.
At the output of the DC/DC , we use Supercaps (1F) to avoid peak current on the battery.
Our choice is to use a DC/DC with a limit current.

My concern is as followed:
We have evaluated the tps63060 with EVM-619 .
The behavior of the component was what we are waiting for.

There is a current limitation and energy of supercaps is used.
On our PCB , current limit is twice (3A) the previous value  when we are charging supercaps at switching on.

We have modified the EVM to have same design.

Behavior of EVM has not change

We have modified the EVM in order to have same design.
behavior of EVM has not changed

we have swapped the IC's between your PCB and the evaluation board.
the behavior follows IC's . there is not link to PCB or design .
I have tried samples from TI store (5) behavior is always the same (3A).

For the moment, I have not eared from TI an explanation why there is difference between EVM and my PCB.

My worry is that I have fitted a design which is not compliant with my application.

And I have validated the design with the EVM.

Have you an idea?

The input current limitation is very important

Christophe

Hi Michael ,
How can I do to share schematic or others data?
I do not want that my design and my application are visible by every one
Christophe

Hi Christophe,

thanks for explaining your application.

I think you would need a device like the TPS61252 Boost converter with adjustable current limit.
The max Vout is 6.5V. Maybe this is enough for your system.

For solving the issue of the TPS63060:

Could you please send me two scope plots measured on our EVM.
First plot with the working unit and the second with the unit with unexpected behavior.
The plots should show Vin, Iin, Vout, IInductor.

please try again to send me the schematic/layout by private E2E message.

Thanks & Regards,
Michael

Hi Christophe ,

Beside of the TPS61252 (Vout max = 6.5V) there is the new TPS61088 which could help here.


thanks for the data. I got the schematic and two scope plots.

Regarding the two scope plots you sent me. Can you describe where and how you measure the current?
Could you also add at least Vin, Vout to the plots? You can post it directly here.

Which typ of battery do u use in your design?

Regards,
Michael

hi Michael?

please find others plots.

batteries used are Li-mno2

Hi Michael, Can we arrange a call to discuss our problem please? Also do you have contact information suitable for passing to our Sourcing and Quality teams please?

Kind Regards

Ruth (Christophe's PM)

Hi Ruth, hi Christophe,

Thanks for the additional data.
Could you please clarify which trace represents which signal and how is the scale (V/div ?)

Basically, what is shown in Figure 7 in the D/S is the DC current limit behavior which applies when the device operates in steady state (no change in VIN/VOUT). This is at least 2.1A or higher, so more than what you would need.

The startup current is as shown in Figure 32 and can go up to ~3.5A (depending on the conditions). This is how the device is designed and it seems to be as well to high for your requirements.

This is the same behavior we see in the lab when we measured your conditions. If you see a current which is completely different, that is not what we would expect.

So there is one Unit that shows a different behavior? And this happens independent of the PCB? Can you please pass us the layout?

Thanks & Regards,
Michael

Hi,

Answers to yor questions:
-Picture 1:
yellow= current probe : 0.1V/A
blue= Vin: scale/10

-picture 2:
yellow= Vout: scale: 1
blue= Vin: scale: /10

-picture 3:
yellow= current probe : 0.1V/A
blue= Vout: scale: 1

-Picture 4:
yellow= current probe : 0.1V/A
blue= Vin: scale/10

-picture 5: sorry, wrong picture: find below the right one
yellow= current probe : 0.1V/A
blue= Vout: scale: 1

-picture 6:
yellow= Vout: scale: 1
blue= Vin: scale: 1

The EVM, we have tested, have the following serial number :
TPS63060EVM-619
HPA619 Rev.C
2011.

the marking code on the part is:
QUJ
TI 39K
D6GB

This means that parts were manufactured before 2011. Do you test with part manufactured at same period?

As i said it is idependent of PCB. These measurements are done on EVM, so you have the layout. The modifications are :
changing R to tune the output voltage at 7.5V
adding super cap (1F) at the output

Christophe

Hi Christophe, so each trace is measured on the evaluation board, but which IC in each instance? Are they all the original evaluation board IC (2011) or are some of the sample ICs please?

Michael, would this be easier over the phone or Skype (so we can share screens)?

pictures 1,2,3 are for the EVM 1 and pictures 4.5.6 are for EVM 2

For EVM 1:
Marking code on the part is:
QUJ
TI 52K
CNQY

EVM reference is:
HPA619 Rev.C
2011.



For EVM 2:
Marking code on the part is:
QUJ
TI 39K
D6GB

EVM reference is:
HPA619 Rev.C
2011.

Christophe

Thanks Chritophe.
As stated, the two Units you refer to are the same in terms of Si-revision. We would expect all of them to behave as in the D/S sections Michael mentioned in his last post.
Due to Units being exchanged and handled a lot, It can appear that they see damages, even if just in several parameters. As of my understanding, there is just one single Unit that shows a lower start-up current behavior.
For TPS63060, you have to expect a current of ~3.5A during start-up, which is way to high for your current limit application.