TPS61071-Q1: What is the difference between TPS61070/1/2/3, TPS61071-Q1

Hi Ohad:

Thanks for asking. You could check the comparison table in datasheet to find the differences. it should be in the Page 3. Besides, "-Q1" means it‘s an automotive rate device.

 You could choose TPS61070 or TPS61071 to do the demo. If there is further questions, just let me know.

Hi Minqiu,

You can be sure that if aplly to you through E2E cause I need that device I have already checked the datasheet and seen that table.

It is very unprofessinal for a TI representative to give me that answer !!!

The facts that frequency is different between TPS61072DDC to the rst and that Power-Save mode is Enabled in  TPS61070DDC do not give me anything.

As an HW engineer when I apply to TI E2E with such a question than I expect to get a much more serious answer which explain in deep the meaning of these differences between the devices on the applications they serve.

Which of them best fits my application which is a Mother Board as I already said connected to external continious power supply and not a battery.

And regard the additional difference "-Q1" , I know to read the a,b,c... exactly as you to read that "-Q1" is recommended for automative.  

Still the question remains the same: what does it mean internally ? and how does it influence the performance and which is more recommended to

my application??

If you do not know the answers please refer it to some one who knows better this area.

Ohad

Hi Ohad:

So sorry for making you uncomfortable. Please forgive me didn't realize you have do a lot effort before you asking and misunderstanding your questions.  Sincerely apology!

These four parts are highly similar parts. And the Table describe the difference clearly.  Is your question is about the details meaning of these difference?

POWER-SAVE MODE: The details is showed in "10.4.1". With the power save mode, the efficiency will be better during the light load but the switching frequency will be change. If you don't care about the efficiency, you could choose disable version.

OPERATING FREQUENCY: It's the typical switching frequency in PWM mode. The high switch could allow to use smaller value external component as inductance and Cout with smaller size. But high frequency may bring more power loss. 

EN THRESHOLD REFERENCE VOLTAGE: The EN signal thresholds are varied. It's base on the Bat or 1.8V logic. The details could check the datasheet "8.5 Electrical Characteristics".

"TPS61071-Q1": This part passes AEC-Q100 Qualified. It's suitable for automotive application. The operation function is similar with TPS61071. 

Let's focus on your application. May I know what it use for? Is it a automotive related usage, or do you concern about the AEC-100 qualified? And what's your load condition? What's the current of the load during the startup and normal operation? Is it care about the noise from converter? Is this converter keep enable for your system? And what's the enable signal you prefer, short to Vbat or controlled by MCU? If controlled by MCU, what's the high/low voltage of it?

Additionally, as this is not a face to face communication, I may misunderstand your point sometime.  It's really glad to support you, and appreciate if you share more details and clear description. Thanks for your kind understanding.

If the question is beyond what I know, I'll ask the further support from my team following TI's process.

Hi Minqiu,

Thanks for the detailed answer, that's what I expected at first :-)

My application is a PCB that sits in a CT Scanner, which means it is in a fast movement while working. That's why I was curious regard the the "automative" issue and wanted to understand what is so special with being "automative" ? Does is it make it more robust when being in a fast movement ? Is it also OK for applications which are not automative or it can cause problems to such appliacation ? What shall fit best my need?  the TPS61071-Q1 or the TPS61071 ?

Regard your questions, as you could see it is not for automotive related usage but it is going to be in a fast movemnet while working.

I'm going to use that up converter twice in my system:

1) In one board it is going to do: 1.9v => 3.5v conversion when load current is about Iout=27mA., therefore according to my calculations I need L=33uH inductor at the input and C=2.2uF in the output .

2) In the second board it is going to do 2.5v=>3.4v with Iout=60mA load. 

In both boards it shall work continiously when Power is on by external Power supply, therefore, Enable signal shall be on whenever power is on connected to Vbat.

Thanks,

Ohad  

Hi Ohad:

So sorry that I'm in oversea travel these days. Please allow me reply next Monday. Thanks for your patient waiting.

Hi Ohad:

Thanks for your patience. 

Firstly, I'm sorry to notice that the "automotive" is means automotive car here. If you has no request of "AQE-100" (A quality standard), then you don't need the part with "-Q1". I thinks fast moving is OK for the IC, if the mechanical setup is reliable.

As your output current is small, you could use a little larger current ripple rate in your calculation. Otherwise, the inductance is too large.

According to your application, I'll recommend the TPS61071 to you. And there are several design suggestion:

1. If there is obvious noise at EN pin, you could add a resistance and small capacitance to filter the noise.

2. I'm not sure if the system is stable using 33uH inductance with 2.2uF. If not, you could choose 10uH and litter larger Cout.

3. Follow the layout guidance when you do that.

8880.Comment_to_TI_E2E.docxHi Minqiu,

Regard your design suggestions :

1. There wasn't any comment on that issue in the datasheet, there was no recommendation to add Low pass filter on the EN input. On the contrary, according to the scheme of the example application in the datasheet, EN is connected directly to VBAT with no ressistance in the middle:

2. You say you are not sure if "the system is stable using 33uH inductance with 2.2uF". Well the only way for me to decide which inductor/capacitor to choose is to follow the formulas given in the datasheet for that up-converter and according to them and to my requirements:1.9v=>3.5v  Iout=27mA :         

and because of that comment in the datasheet :

the chosen capacitor was : 2.2uF

I chose the values for Inductor and capacitor for the up-converter according to the recommendations in the datasheet for my requirements,

So please explain to me why you think these values create an "Un-stable" system ? according to what you said.

3. LayOut guidelins will be taken in consideration in LayOut.

Thanks,

Ohad

Comment_to_TI_E2E.docx

Hi Ohad:

Thanks for your details description. For your concern, please see my clarification. 

1. For the EN pin, what I want to say is "If there is obvious noise". The level of noise depends on your system. If your power supply always works well with high performance, just connect the EN pin to BAT.  

2. Yes, there is a guidance showing how to select inductance. But for your application, the load is very light. So that's why I recommend to use a larger current rating (in your calculation, it's "40%".) Other wise you will choose a larger value inductance. It's not a good choice for the size and cost.

For the stable concern, our device has compensation circuit inside. As it mentioned in datasheet: "The device has been optimized to operate with inductance values between 2.2 μH and 10 μH. Nevertheless, operation with higher inductance values may be possible in some applications. Detailed stability"

I just point out there may be a risk. It doesn't mean the system "must" be unstable with such components. 

Hi Minqiu,

Shall I understand from your answer that my application has a too small load for the  TPS61071-Q1 normal operation and therefore do I need a different Up converter , which fits better my application ?? (Iout=27mA and it may be even smaller), you saw the formula).

Thanks,

Ohad

Hi Ohad:

TLV61220 has the smaller current capability but your load condition is near the boundary. So I'll still recommend the TPS6107x family. The TPS6107x family could support smaller current load well.

If you choose 40% into calculation, it requires larger value of the inductance if the switch frequency is fixed. And may I know you have some special requirements about current ripple?

Hi Minqiu,

No special requirements.

Ohad

Hi Ohad:

If there is no special requirements, I'll suggest use 10uH inductance with 4.7uF*2 Cout. Both TPS61070 and TPS61071 could work. The major difference is TPS61070 has better efficiency, while TPS61071 has constant switch frequency. As you may don't care about the efficiency, so the TPS61071 is the better choice.

After all, it's just suggestion. You could choose the parameter you prefer, and I'm always glad to offer further support. 

Hi,

What ??? Now I don't understand you at all !

I told you before that the requirements of my up converter are :

Vin: 1.9v, Vout: 3.3v, Iout=27mA and and as you know f=1200MHz. I answered to your question regard any special requirements for the Delta IL that there is no special requirement to that.

I showed you in my last response my calculations according to the formulas apear in the TPS61071-Q datasheet from which it turns that: L=33uH, Cout=2.2uF.

How come you say now you suggest L=10uH and Cout=4.7uF ???  I don't understand you at all... 

It looks like either you are confused or you didn't understand anything of what I wrote ...

Can you please treat my case more seriously  and if you do not understand this datasheet and its formulas please refer this issue to someone who do understand.

Ohad

Hi Ohad,

sorry for jumping into your discussion. I want to share my opinion about the inductor and capacitor selection.

the equation to calculate the inductor in the datasheet does confuse for converter device (fully integrate the MOSFET and compensation), especial when the output current is small. so I wrote this application note before to explain this problem. 

http://www.ti.com/lit/an/slva797/slva797.pdf 

about the capacitor selection, we need to consider the stable ripple, load transient performance and stability. from the stable ripple, small capacitor should be Ok at only 27mA output, but the stability and transient performance also need to check. the datasheet also suggest capacitance is verified by simulation and bench test to convenience user.

Hi Jasper,

So I want to get that straight once : Are the formulas in the TPS61071-Q1 datasheet recommended to calculate the Inductor/capacitor according to the Vin,Vout,Iout ?

The previous representative didn't make that issue clear ... after he kind of confirmed my calculations using these formulas he told me he sugget to pick other values, so I don't understand what is your recommendation as the representatives of TI - the vendor of that Up converter...

So I ask it once again to be sure I understand you correctly :Shall I use the formulas given in datasheet for defining : L,Cout, Rout values or not ?

It is very important to me to get a clear and correct answer since I use it in a new Mother Board I desgin and I don't want to face any current problems or EMI/EMC problem later.

Please   let me know.

Thanks,

Ohad

Hi Ohad,

the most safety method is following the components suggested in the first page of the datasheet or the Figure 20. the circuit cover output current from 0 to 100mA.  however, it may be not the most optimized.

 if you want to further optimize the external components to get a small improve in efficiency and cost. you can use the formula to calculate the external components, then select a value within the limitation setting the description. however, you would need to check the stability of the circuit.