Question about thermal consideration of LTC7124

Hello,

My customer is useing LTC7124 , but they have some issue about heat.

So they want to reduce the heat value from LTC7124.

For reducing the heat value, they think that that if load are dispersed, heating value will be reduced.

So they mesured temperature of LTC7124 top side with below conditions.

But the test results are different from their guess. ( In case of dispersing load, temperature of LTC7124 top side is high.)

Condition 1:  2MHz Continuous Mode / Dual output

       1 Port =>  Input Volt : 12V,   Output Volt : 3.3V,     Load : 1.5A

       2 Port =>  Input Volt : 12V,   Output Volt : 3.3V,     Load : 0A 

Condition 2: 2MHz Continuous Mode / Dual Phase Single Output

        1,2 Port =>  Input Volt : 12V,   Output Volt : 3.3V,     Load : 1.5A

Test Results:  Temperature of top side at Condition2 is higher than emperature of top side at Condition1

Q1. Would you confirm above test result?  Is Above Result right?

     ( As the fomula in Thermal consideration of Datasheet, power dissipation of condition 1 is bigger than that of condition1.)

Q2. Would you let us know why temperature is high when load is dispersed?

Q3. Would you advise how to reduce heating value of LTC7124 at below condition?

     Vin 12V / Vout 3.3V/ Iout 1.5A / 2MHz PWM

Regards,

Se-woong

Parents Reply
  • +1
    •  Analog Employees 
    on Apr 14, 2021 9:27 AM in reply to Se-woong

    Hi Se-woong,

    I assume testing is done not using ADI demo board. Am I correct? It may help if you can provide schematic.

    Two channels in condition #2: make sure to do good paralleling. Please refer to page 19 of datasheet: schematic. For total 1.5A, the circuit might run in burst mode. It is possible that if the load current is not balanced, and both channels are actively switching to FCM mode, the loss will be higher.

    With 1.5A total load, it is best to let it run in single channel if running in FCM.

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