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# LTM4607

Category: Datasheet/Specs
Product Number: ＬＴＭ4607 Rsense calculate

Hi

I am DFAE in Japan.

Our customer is designing LTM4607.

But we can not understand to calculate Design examples of  Rsense.

At Buck mode operation

Vin=12V to 36V, Vout=12V, f=400kHz,P=120W(Iout=10A) η=0.95 L=4.7uH

So, Iout=IL=120W/(12V) =10A.

ΔIL=10Ax(36V-12V)x12Vx12V/(36Vx4.7uHx400kHzx120W)=4.26A

Rsense=2x0.13/(2x120W/12V-4.26A)=16.5mΩ

But data sheet mention 9mΩ. Can you tell me how to calculate 9mΩ?

I can not undesstand how to caluculate 30% safety margin.

At Boost mode operation

Vin=5V to 12V, Vout=12V, f=400kHz,P=60W(Iout=5A) η=0.95 L=3.3uH

So, Iin=IL=60W/(5Vx0.95) =12.63A.

ΔIL=12.63Ax(12V-5V)x5Vx5Vx0.95/(12Vx3.3uHx400kHzx60W)=2.21A

Rsense=2x0.16x5V/(2x5Ax12V+2.21Ax5V)=12.2mΩ

But data sheet mention 7mΩ. Can you tell me how to calculate 7mΩ?

Best regards

N.Kokubo

## Top Replies

+1 verified

Hello,

This means that you should lower your value to about 30% for the computed one to have an allowance for non-ideal characteristics.

for a 30% safety margin:

16.25*0.7 = 11.375 mOhms.

It might be…

Parents

Hello,

This means that you should lower your value to about 30% for the computed one to have an allowance for non-ideal characteristics.

for a 30% safety margin:

16.25*0.7 = 11.375 mOhms.

It might be that the closest available one is 9mohms compared to the computation.

The same case for the boost mode.

12.2*0.7 = 8.54 mOhms.

The closest value available might have been 7mohms.

Generally, a safety margin is considered to allow for variations, parasitics, and tolerances of the components.

Regards,

Jhun

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