Other Parts Discussed in Thread: CSD18503Q5A
Dear Mr/Mrs
In the datasheet for the TPS2482 at page 23/59
2. Choose Pass-MOSFET, M1
in equation 6
RϴJA = 31 °C/W
How is this number 31 choosen ?
With kind regards
Marcel
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Dear Mr/Mrs
In the datasheet for the TPS2482 at page 23/59
2. Choose Pass-MOSFET, M1
in equation 6
RϴJA = 31 °C/W
How is this number 31 choosen ?
With kind regards
Marcel
Hi Marcel,
Thanks for reaching out. It is obtained from the thermal performance of EVM.
In equation 4 you calculate 4.17 mOhm on page 23/59
Then you choose 3mOhm in stead of 4 mOhm. Should you not calcaulate the Max current based on the choosen sense resistor ?
So when I choose 4 mOhm you get a current of 10,41666667 A
In equation 7 how is the RDS choosen of 6.45 mOhm ?
I take a look in the datasheet CSD18503Q5A page 1 of 3
RDS(on) Drain-to-source on-resistance VGS = 4.5 V 4.7 mΩ so 4.7mOhm times 1.39 taken from figure (graph) 8 Normalized On-State Resistance vs Temperature @ 100°C
gives 4.7 mOhm x 1.39 = 6.533 mOhm ?
With kind regards
Marcel
Hi Marcel,
Please go through these videos and app note.
https://training.ti.com/node/1133677
https://training.ti.com/node/1133673
https://training.ti.com/node/1133664
Design calculator with equations shown is NDA restricted. I can't share in a public forum. Please provide your design calculation sheet. I will review and get back to you.
Hello Avishek Pal
For now I am following the example in the TPS2482 datasheet om page 24/59
For CSD18503Q5A, ZθJC of 0.3 can be used for fault times below 10 ms. I dont understand how you get to this number?
Using this datasheet
figure 1: Transient Thermal Impedance. I assume the Single Pulse Line. I look at the x-axis tp Pulse duration at number 0.01 = 10ms long pulse.
Then I look where this line crosses Single Pulse line and read out the y-axis ZθJC Normalized Thermal Impedance is about 0.8 times RθJC.
In the TPS2482 datasheet a number of 0.3 is mentioned what would be corresponding with a 1ms single pulse.
With kind regards
Marcel Loos
Hello Avishek Pal
For now I am following the example in the TPS2482 datasheet om page 24/59 section
3. Choose the Power Limit, PLIM, and the PROG Resistors, RPROG1 and RPROG2
How is ZθJC choosen ?
In the graph for the CSD18503Q5A I see a value of ZθJC = 0.8 at 0.01 (s) Pulse duration (10ms)
In the graph for the CSD18503Q5A I see a value of ZθJC = 0.3 at 0.001 (s) Pulse duration (1ms)
On page 25/59
4. Choose the Timer Capacitor, CT
In this section they calculate Ton(max) = 1.58ms, on the graph in between 0.001 and 0.002 (s) I read a value ZθJC = 0.4
In this section they calculate tFault = 6.6 ms, on the graph in between 0.001 and 0.01 (s) I read a value ZθJC = 0.8
Is what I am doing correct?
With kind regards
Marcel Loos
Hi Marcel,
It looks correct to me. Selection of power limit is a recursive method. You may refer to this E2E blog for a better understanding of transient thermal impedance.