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# TPS62933: TPS62933 - inductor select

Part Number: TPS62933

Hello.

I working with TPS62933DRLR for one power supply. My load have the characteristic operating with 100mA constant and 1A pulsed. Similar to radio.
In webench, my simulation recommend use one inductor 3.3uH with 9A pico. Buth when I calcuculate follow the datasheet, my inductor result 3.3uH with 2A pico.

What is the difference ? Does the simulator have any safety margins or any specific details? I´m operating with 2.2MHz, my input range is 5V to 30V and output voltage is 4V.

• Hi  Romulo

Just to confirm that the input of your application is 5V to 30V? Why does the input have such large range? May I know your end equipment and the TAM?

Actually, when designing the inductor, we consider the max loading as 3A, and then choose the current ratio K (0.2~0.6 recommended). After that, we will choose the peak value to avoid saturation.

As Vin rises, the peak value of the inductor current will be increased, as a result, you may consider the max Vin after choosing an inductor's value.

Hope this helps.

BR

Ruby

My source project was done in a generic way, as it needs to operate in three different input ranges, 5V to 15V, 9 to 24V and 12 to 30V.

In my calculations, I considered K = 0.4, Fsw 2.2Mhz, input voltage 30V and current 1A.

The calculation resulted in 4.3uH.

My Delta IL 0.4 [A] results, IL 1.2 [A] peak results, and IL RMS 1.01 [A] results.

So can I consider my 4.3uH inductor with what peak current and saturation current?

Maximum current consumption [1A] + Peak current [1.2A]+ Safety margin [30%]? 2.86A +- 3A saturation ?

• Hi Romulo

1. "considered K = 0.4, Fsw 2.2Mhz, input voltage 30V and current 1A", please consider the current 3A for the inductor calculation, since our compensation is fixed within the device and we consider the 3A for the design. As a result, when you choose K=0.4, please use 3A for the calculation.

2. Regarding the input 30V, do you mean that the constant input value could be 30V? I am wondering if there is any chance that the input has spike when Vin=30V. Our device is a 30V device, if the spike is over 32V, there is a risk to damage the device.

3. 2.86A+3A is good for the design.

Hope this helps.

BR

Ruby

• Ok, I will use 3A in my calculations

About the risk of a peak greater than 30V, I will consider it.