TPS61196-Q1: Low Temperature Shutdown ISSUE & Schematic review

Hi CHO,

We need some waveforms to find out the root cause for this issue. As for schematic review, I will give you feedback on 08.17th.

Hi CHO,

Why two of your output capacitors are connected to DGND rather than SGND?

Hi Charles

 Waveform

1. Normal operation at low temperature(Ch1 : EN , Ch2~4 : FB 3Ch)

2. Low temperature Shutdown(Ch1 : EN, Ch2 : Fault, Ch3~4 : FB 2ch)

DGND, SGND

DGND & SGND are not separated.

Hi CHO,

We recommend to connect these two output capacitor to SGND directly rather than through 0 ohm resistors.

According to your waveforms, some faults happen in low temperature and your controller pull down the EN so that the device is shut down. So we need to find out which faults happen next step. Can you provide additional waveforms to find out the specific faults? For example, the output voltage, the input voltage, the node of SW, the current of inductor or the voltage of ISNS.

We also have protection list at page 17 of datasheet and you can try to find some abnormal waveforms according to each item.

Hi Charles 

The customer is preparing a waveform.

Is there any problem with the value of cap & register according to the schematic review?

Waveform

Ch1: VIN, Ch2: ISNS, Ch3: FBP, Ch4: FB1

Ch1: ISET, Ch2: FSW, Ch3: IFBV, Ch4: FB1

Hi CHO，

Sorry that I don't describe the waveform requirements clearly. Actually, I actually need the waveform at the following point when faults happen.

Besides, do you have corresponding FAE for your customer?

Hi Charles 

Sorry, I asked the customer for the waveform again, but it has not been obtained yet.
The FAE will visit the customer company tomorrow to confirm.

Hi Charles,

Please review below answers and information.

1. The input value of VIN in the previous mail is 13.5V and the Vout is 13V through D1(in the fault condition)

 7331.Wavefrom.zip

2. Reviewed information

a. ISET = 51K, it was set approximately 96mA(in Duty=100% condition) and actual usage is 58mA in duty=60% condition

b. IFBV = 39K, VIFBV is set as 235mV

c. In the below picture, Headroom Voltage is 235mV and assumed that it was in over current condition

d. Over current Spec. was decreased in accordance that VIFBV voltage value was going down as a result of test(Temp.: 35, 0, -10 and -20)

e. Thus, No boost up because it was recognized as over current in test temp. -20.

f. Confirmed that the sample which was not boosted up in low temp was working in accordance with adjusting IFBV

Actual current used: 58 mA to 65 mA                                                                     Low temperature: HV voltage goes down, over current recognition

3. Requirement

a. The difference of output voltage is around 40mV in IFBV according to temp., changes from 35 to -20.

     Could you please explain the reason why it has changes according to temp. of IFBV

     *Resistance error rate which was applied to samples is F grade.

b. Please confirm whether we can use the values of schematic.

Hi Charles

Thank you.

The answer is delivered to the customer, visited and explained.

I would like you to give me a detailed explanation of the additional inquiry.

The difference of output voltage is around 40mV in IFBV according to temp., changes from 35 to -20.

Could you please explain the reason why it has changes according to temp. of IFBV

 *Resistance error rate which was applied to samples is F grade.

Hi Charles

We explained to our customers as follows.

1. 235mV applied by IFBV voltage setting range (300mV to 1V) has a problem with the setting.

2. Drops of 40 mV occur in IFBV at low temperature (-20), and the proposed margin design is presented as an improvement method.

3. Customer sets IFBV value to 350mV and performs cold test again

* Customer requirements
Q1. IFBV Voltage vs. operation temperature

 - TI feedback such as graphs or related documents to check IFBV voltage deviation due to temperature, or comments for reference

*** We want to receive relevant data by early next week. Please give us your urgent support.

Hi CHO,

What about the result after setting IFBV value to 350 mV?

For graphs or related documents to check IFBV voltage deviation, I don't have the data at hand right now and perhaps there are no relevant data. I need to check this with my team.

What about the result after setting IFBV value to 350 mV?

-> The test results have not yet been updated. Update when the test results are communicated.

Hi CHO,

OK.