SN6507-Q1: Current calculation

Danilo A.

Mastermind 32065 points

Part Number: SN6507-Q1
Other Parts Discussed in Thread: SN6507

Hi Team,

Posting on behalf of our customer.

I will share this E2E post to our customer so he can reply when needed.

Currently, our project uses TI’s SN6507+SM91208L.

1、We need to evaluate the currents flowing through the SN6507 SW1&SW2 switch drive currents when driving the transformer.The current specified in the datasheet currently does not include the drive current. Please help assess how to evaluate it

2. Please provide the current calculation formulas for SW1 and SW2, along with the meanings of the variables. Also, please help calculate the current for our product (designed for 12V input, 15V output; f=1MHz);

3. Please provide your internal current test results, current waveform diagram, and calculations for the SN6507 chip;

4. Is the input current of the SN6507 related to the current at the output load?

Regards,

Danilo

1 month ago

0 Prateek Verma 28 days ago

TI__Prodigy 640 points

Hi Danilo,

I will test the EVM and provide you the current test result.

Thanks

Prateek

0 Prateek Verma 12 days ago

TI__Prodigy 640 points

Hi Danilo,

Please find below input.

1. How the switch node current looks like is mentioned in the datasheet in Figure 8-4. I have attached a Screenshot of that below. The switch node current would depend on the load connected at the output.

2. The formula to calculate SW node current is very well explained in this video.

https://www.youtube.com/watch?v=kT1gvTmK1TE&list=PLGjyOARIhfLpjA6PoM7B65sd8cdEqJQWv&index=4

3. Below is the switch node current waveform at SW1(ch3) and SW2(ch4).

4. Yes the input current of SN6507 is related to the current at the output load and is directly proportional to it.

Pls let me know if you any questions.

Thanks,

Prateek

0 Panwei Lv 12 days ago

Prodigy 30 points

Hello as we cannot access to Youtube easily in China, is there any other source of the vedio available?

https://www.youtube.com/watch?v=kT1gvTmK1TE&list=PLGjyOARIhfLpjA6PoM7B65sd8cdEqJQWv&index=4

0 Panwei Lv 12 days ago in reply to Prateek Verma

Prodigy 30 points

and could you help to directly calculate the current for our product (designed for 12V input, 15V output; f=1MHz)？

0 Prateek Verma 11 days ago in reply to Panwei Lv

TI__Prodigy 640 points

Hi Panwei,

I can send the video to you over email. let me know your mail -id.

Current at SW would depend upon transformer turns ratio and its magnetizing inductance. Which transformer are you using ?

Thanks,

Prateek

0 Panwei Lv 8 days ago in reply to Prateek Verma

Prodigy 30 points

panwei.lv@forvia.com and also to our HW: jie.he@forvia.com

0 jie He 8 days ago in reply to Prateek Verma

Prodigy 50 points

For detailed current calculations, I hope you can provide examples using formulas based on the parameters I provide, showing the SW node current under no-load and 150mA load conditions.

0 jie He 8 days ago in reply to Prateek Verma

Prodigy 50 points

We are using SN6507+SM91208L_E

0 Prateek Verma 8 days ago in reply to jie He

TI__Prodigy 640 points

Hi Jie,

Thanks for providing the details. I will update you as soon as I calculate the current at SW.

Thanks,

Prateek

0 jie He 6 days ago in reply to Prateek Verma

Prodigy 50 points

Hello, has the calculation been completed? How long will it take to receive the results?Hello, has the calculation been completed? How long will it take to receive the results?

0 Prateek Verma 6 days ago in reply to jie He

TI__Prodigy 640 points

Hi Jie,

Please find the below sources for detailed calculation of Current waveforms at SW.

1. Chapter 14 in this handbook - https://www.ti.com/lit/eb/slyu036a/slyu036a.pdf?ts=1772520506279

2. You can also use https://www.ti.com/tool/POWERSTAGE-DESIGNER to calculate values directly and see waveforms

Thanks,

Prateek

0 jie He 20 hours ago in reply to Prateek Verma

Prodigy 50 points

Hello, Please help me answer the following questions.

1、I don't quite understand the formulas in the PDF. Could you please provide a detailed formula for calculating the SW node current and help me calculate the SW node current under no-load and 150mA load conditions based on the circuit parameters I provided?

2、Circuit application: SN6507 + SM91208L_E are used; input voltage 12V, output voltage 15V. The above are my circuit design requirements and parameters. Since I need to calculate the input current, please help me derive and calculate the input current in detail using the formula when the output current is 0A and 150mA (derivation process and calculation values are required).The yellow section below is the current I need you to calculate.

3.What is the relationship between the center tap current (marked in yellow) and the currents of switches SW1 and SW2? Is the center tap current (marked in yellow) equal to the sum of the currents of SW1 and SW2? How are the currents of SW1 and SW2 calculated? Please provide the formulas for calculating the currents of SW1 and SW2, as well as detailed calculated values for SW1 and SW2 when the output currents are 0A and 150mA respectively (the derivation and calculated values should be based on my circuit parameters).

4.Below are my detailed schematics. Components marked in red are unmounted. Please help calculate the SW current based on the schematics and application requirements I provided.

0 Prateek Verma 16 hours ago in reply to jie He

TI__Prodigy 640 points

Hi Jie,

Give me two days, I'll get back to you with the calculation

Thanks,

Prateek

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SN6507-Q1: Current calculation