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Resistor and frequency relation EN63A0QA

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Hello,

 

I would like to know the exact relation between resistor for frequency adjustment and the frequency for EN63A0QA. Table1 and 2 of the datasheet recommended some value but I don't know which frequency is used.

 

Thanks

Regards

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Hi Matt,

 

The frequency can be adjusted by the Rfadj as in the attached chart.

 Freq.PNG

Regarding the stability: yes, type IV is almost the same as type III (with extra pole and Zero) and it is just a one control loop, please follow the datasheet recommendation regarding the feedback loop component to maintain the system stable.

 

Regards,

Mostafa

 

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EN63A0QA Switching Frequency designed for 0.9MHz to 1.5MHz ,I believe your frequency should be between those values. Table 1 and Table 2 is the tuned optimized value based on performance and Efficiency. I think Table 1 and Table 2 covered for all the input @ 10 A and 12 A. Can you tell me are you looking for any other specific input ?

Note : Switching frequency are based on min Duty ON time requirement ,Stability and Component package sizes. The reason i brought up this point because for RFQADJ 3.57Kohm @3.3V input ,Vout = 0.8V for the load current of 10A ,it will definitely work for less load current.

 

Thank you ,

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Yes table 1 and table 2 covered all input (mine is 0.8V 0A to 12A) but in my application I need to know which frequency is used in order to be sure that no interferences with other system could arrive. And, I would like to have the capacility to adjust a little (more or less 100 KHz) the frequency to avoid any issue without the use of an external clock.

 

About the stability, the datasheet says it use a type IV compensation but application note #103 speaks abut a type III compensation, so what type is used?

 

Thanks

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Sure ..As of My understanding about this device is designed for particular frequency band based on input voltage ,output voltage and load current.For interference problem i would suggest to go for PCB Layout /Placement /Avoid high current big loop/grounding technique not frequency.

Stability : Type III compensation is best bet , if you see the graph of Voltage vs change in Output current (0 - 8A) Figure 4 shows , Poles and Zeros are perfectly placed. My suggestion would be start with type III, calculate the RC value for your load current (Note given app note is for 8A load) . Once board design done , you can either measure stability using power analyzer or Manual Method.Then try it out with Type II ,Since it is very high load I dont know it will converge in type II but you can always try.

 

Thank you.

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I agree with you about PCB to avoid high current big loop but about EMC signature, I really need to know the frequency of the component. For exemple, if we have a lot of functions using the band around 1MHz, I need to know which function use which frequency. I'm sure that there is a simple relation between resistor and frequency and I need to know it.

 

About stability, my question was related about the datasheet. It is written that "The feedback control loop incorporates a type IV voltage mode control design". Is it just to say that we can use a type III or type IV compensation or is it another sense (like a second loop inside the component)?

 

Thanks.

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Employee
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Hello MBaqu,

 

EN6360QA has two ways to adjust the switching frequency:

  1. Using RFQADJ, and you can select its value form Table 1.
  2. Using external clock, and you can select its optimized frequency from Table 2.

 

In your case, the output voltage is 0.8V so,

  1. If you use the resistor to adjust the frequency, the resistor value will be 3.57kohm.
  2. if you use external clock, its frequency has to be 1.15MHz.

I hope that I could answer your question.

 

let me know if you still have any inquiry.

 

Thanks,

Shimaa

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Hello Shimaa,

 

In my case, I will use RFQADJ instead of external clock.

By reading your answer, I saw that I made a mistake on my initial post, my voltage is 0.85V, not 0.8V but I assume that resistor will be also 3.57Kohms.

 

So, I understand that frequency will be 1.15MHz with this value, right? I'm sure that this frequency is the best choice for this output voltage because it's the value recommended by Intel but my question is the same, if I want to move this frequency (for exemple 1.1Mhz), I need to know the relation between RFQADJ and frequency. to choose the right value for RFQADJ.

 

I don't understand why this relation isn't provided.

 

And about stability, do you have answer?. In the datasheet it is written that "The feedback control loop incorporates a type IV voltage mode control design". Is it just to say that we can use a type III or type IV compensation or is it another sense (like a second loop inside the component)?

 

Regards

Matthieu B

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Hi Matt,

 

The frequency can be adjusted by the Rfadj as in the attached chart.

 Freq.PNG

Regarding the stability: yes, type IV is almost the same as type III (with extra pole and Zero) and it is just a one control loop, please follow the datasheet recommendation regarding the feedback loop component to maintain the system stable.

 

Regards,

Mostafa

 

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Beginner
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Beginner
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Hello saudr,

 

Could you explain more about difficullties with this component?

 

Thanks

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Hello Saudr,

 

I didn't understand your post, could you please give more information so I can help you.

 

Thanks,

Mostafa

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