TPS25924: About Design-Calculator(EXCEL)

Hi Rakesh,

Thank you for your quick support.

Q1A) "RIstart" is a pure resistance

I understand.

Q2A) "RIstart" corresponds to load resistance value at the instance the rated voltage is applied across the load

Is my understanding of the rated voltage = VIN(max) correct?

Q3A) One way to get the load resistance is to measure V-I characteristics of the load by powering from a bench power supply

Is the power supply behind eFuse, but is it possible to measure the VI characteristics?

Can you please let us know the end equipment and system requirements

equipment:ROUTER
system requirements:
TPS25924
VIN(max):12.6
UVset:8
Cout:540uF
RIstart:4ohm(Unmeasured)
Imax:3.5A
Ilimit:4A

Best Regards,

watanabe

Hi Rakesh,

I got questions from the customer.

Q1.

At power on, current of 60A/300μs flows.(Figure 1)

Can I regard it as a spike-like capacitive current?

(It is difficult to calculate the load at power on from this waveform.)

Figure 1

Q2.

The maximum load current is 1.5A(max).

Is the idea of RIstart 12.6V(VIN)/1.5A(max)=8.4Ω correct?

Best regards,

Watanabe

Hi Rakesh,

I got another question from my customer.

Q.

When Total power dissipation at start-up is 11.86 W,
How much ambient temperature can be used?

The design calculator D50cell Total power dissipation at start-up is 11.86 W,
D52cell is NO.

When the ambient temperature is 125 ° C.,
I think that Total power dissipation means exceeding Max power dissipation allowed.

However,
When the ambient temperature is 125 ° C or lower,
it is considered usable.

For your information,
we will post an image of Thermal Shutdown Limit Plot and Calculation Sheet.

Best Regards,

Watanabe

Hi,

I understood that I can operate at 85 ℃.

Attach the Design Calculator.

The maximum operating ambient temperature is 85 ° C.

TPS2592xx-Design-Calculator-RevA_solbox_20170329.xlsx

Best Regards,

Watanabe