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OPA2891: difference in temperature rise

Yuta Nishie
Genius 5190 points
Part Number: OPA2891
Other Parts Discussed in Thread: OPA2156,

Hi,

Why does the IC temperature rise more easily with OPA2891 than with OPA2156 (both SOIC packages)?

Using the same circuit, I input a 25kHz square wave at ±5V. (The power supply is ±15V). After a while, the OPA2156 was about 30°C, while the OPA2891 was about 60°C. What causes the difference in temperature rise?

Best Regards,

Nishie

  • +1
    TI__Mastermind 29615 points

    Hello Nishie,

      The devices have different quiescent current (Iq) values and thermal resistance values. It is true that they use the same package, but thermal resistance values will still differ a bit between devices. 

      Therefore, estimated heat dissipation of the OPA2156 at +/-15V at ambient temperature and without knowing your load current is around: 25C +(119.2C/W*0.264W) = 56C and for the OPA2891 is around 25C +(120.6C/W*0.45W) = 79C. 

    Thank you,

    Sima

  • 0 in reply to Sima Jalaleddine
    Genius 5190 points

    Hi Sima-san,

    Thank you for your supply.

    I apologize for my lack of understanding.

    Could you tell me the calculation method of 0.264W and 0.45W used when calculating heat dissipation? Did you multiply the current consumption by the power supply voltage?

    Best Regards,

    Nishie

  • +1 in reply to Yuta Nishie
    TI__Mastermind 29615 points

    Hello Nishie-san,

      No worries, you are correct! It is from 2-channel current consumption multiplied by the power supply voltage. For the OPA2156, it would be 4.4mA * 2 * 30V = 0.264W. And for the OPA2891, it would be 7.5mA * 2 * 30V = 0.45W.

    Thank you!
    Sima