SM72445: 'SM72445' Inquiries about abnormal operation at low power.

Grady Lee

Part Number: SM72445

Hi, TI expert.

A customer company is developing it using 'SM72445', but in case of low power, an abnormal operation occurred and inquired.

The circuit is said to be configured the same as the EVM Board in the attached file.

The contents of the inquiry are as follows.

* When input 45V is applied, the following waveform is measured.

* 1V is measured on the VIIN pin of SM72445, causing abnormal operation at low power.

It is said that the same phenomenon occurs on the EVM Board. (See waveform below)

We request a software solution review for this issue.

- AIIN pin voltage floating phenomenon related

- Each Analog Value Offset can be set in Reg4 by using I2C.

- I looked up the contents of the field, but there is no other content other than the above.

(Questions)

1. Is it 8bit hex data, can I understand 1bit as 5V / 1024 Sampling?

2. Is 8bit Data Unsigned? Is it Signed?

3. Is there a way to give -Offset?

Please check and reply.

Please tell us if you have any further questions. Thank you.

Comment_SM3320-RF-EV_Schematic.pdf

over 4 years ago

0 Youhao Xi over 4 years ago

TI__Guru* 76205 points

Hi Grady,

Thank you for posting. Would you please clarify what is exactly the problem? Could you tell what is the load condition when the customer measured the above waveform? It is supposed to be a CC or CV load. Please specify the CC or CV setting.

Thanks,

Youhao Xi, Applications Engineering

0 Grady Lee over 4 years ago in reply to Youhao Xi

Genius 3465 points

Hi, Youhao Xi

Thanks for the answer.

We will reply after inquiring to the customer.

0 Youhao Xi over 4 years ago in reply to Grady Lee

TI__Guru* 76205 points

I am looking forward to the info from your customer.

Thanks,

Youhao

0 jiwon shin over 4 years ago in reply to Youhao Xi

Prodigy 40 points

Hi, I'm Questioner in this question.

I usually use cc load, but that's no matter.

Because regardless of load occurs this problem.

Applying only the VCC voltage, the SM42445 current sense input pin occurs voltage.

So, Sensing problem occurs at low power.

To check if it's a circuit problem, I also measured all connection removed AIIN and measured the same like below picture.

Both AIIN and AIOUT output same voltage.

But when sensing circuit connect, we check below picture.

As a result, I wonder why SM72445 current sensing input occurs voltage.

0 Youhao Xi over 4 years ago in reply to jiwon shin

TI__Guru* 76205 points

Hi Jiwon,

What is the input source? Could you show me a picture of it?

Thanks,

Youhao

0 jiwon shin over 4 years ago in reply to Youhao Xi

Prodigy 40 points

I attached our simulator picture.

But i think..it's no problem..

0 Youhao Xi over 4 years ago in reply to jiwon shin

TI__Guru* 76205 points

Thank you for the info. It explains. You should not use a dc power supply at the input. The SM3320 is an MPPT circuit, and it requires a solar panel or a simulator. A dc source simply defeat the MPPT algorithm of the LM72445. In short, our test condition and method is not correct.

Please test the SM3320 with a PV simulator or a real solar panel. It has a particular I-V curve for the LM72445 to operate properly.

Thanks,

Youhao

0 jiwon shin over 4 years ago in reply to Youhao Xi

Prodigy 40 points

The Sorensen device of picture is PV simulator.

We are solar inverter development company.

0 Youhao Xi over 4 years ago in reply to jiwon shin

TI__Guru* 76205 points

Hi Jiwon,

Sorry if I mistook the input source, but I searched Sorensen DCS80-15E on the web, it showed as a dc power supply:

https://www.ntecusa.com/3372_DCS%20series.pdfdocs/

Are you sure it is a PV simulator?

Thanks,

Youhao

0 jiwon shin over 4 years ago in reply to Youhao Xi

Prodigy 40 points

We use TERRSAS program.

Also, we tested one the real solar panel and got the same result.

0 Youhao Xi over 4 years ago in reply to jiwon shin

TI__Guru* 76205 points

Hi Jiwon,

Thank you for the info. I need to check if the AIIN and AIOUT has some active circuit inside. I just know it has ADCs inside but there may be some active circuit turned on during the sampling time. This may take some time to find out because it is an legacy device. However, I do not think this will affect the mppt performance.

Thanks

Youhao

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SM72445: 'SM72445' Inquiries about abnormal operation at low power.