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Original question:

TPS57160-Q1: Output pin shorted to supply line - any problem

TPS57160-Q1: Frequency setting and I out clarification required

Srinivasu V
Intellectual 360 points
Part Number: TPS57160-Q1

Hello,

I want few clarifications for TPS57160-Q1 design,

Our design is - Vin : 18 to 32V and Vout 15V/1.5A. 

1. As per the frequency selection equation(8 and 9), I am getting high range frequency. Please let me know, What is recommended frequency for my requirement?

2. in the datasheet mentioned, current limit threshold  Min: 1.8A and typical : 2.7A @ 25°C and Vin 12V. for Vin 32V and 1.5A current, @ what temperature, we have to consider 1.5A ?

3. Typical current limit given 2.7A. If, I load 2.5A current, what will be the  impact to the IC?

 

4. In datasheet mentioned , Thermal shutdown @ 182°C. but, operating junction temperature mentioned max. 150°C. What will be the condition of the IC  between 150°C to 182°C.?

Thank you,

Srinivasu

 

  • 0
    TI__Mastermind 27470 points

    Hi :

    1. for frequency, equation 8,9 is make sure when Vin is high, and Vo is smaller, higher fsw will lead smaller on time. but for your case, I will suggest you choose low frequency because the high side mosfet working in the high duty which taking the major power loss especially in low Vin, so prefer 300Khz-400Khz

    2. Figure 3 shows that the current limit will decrease by temperature, so higher temp will lead lower current limit. currently , I don't have data shows the relationship between Vin and current limit, normally higher Vin  will lead higher over current limitation

    3. for current limit 2.7A, it should be the peak current of inductor, if load come to 2.5A , with ripple of inductor , it should very close to OCP point

    4. when environment temp is high like 105deg C, and power loss of IC is high (high frequency , high Vin and high duty), it may come to OTP point.

    Thanks

    Daniel Li 

  • 0 in reply to Daniel Li14
    Intellectual 360 points

    Hello Daniel Li,

    Thanks for inputs!.

    Do you have current vs Temperature graph?

    I am finding in the data sheet.

    Thank you,

  • 0 in reply to Srinivasu V
    TI__Mastermind 27470 points

    Hi:

    we don't have the Io VS Temperature raise graph, but if you use 4 layer PCB and has enough PCB for thermal dissipation, the practical Theta Ja will be around 30deg+-20% C/W. Assume the power loss based on the efficiency curve is 1.65W(3.3V 2A 80% efficiency) , the temperature raise will be around 49.5deg C.

    Hope it helps.

    Thanks

    Daniel Li