SBOS789C August 2017 – February 2020 OPA2810
The OPA2810 does not require heat sinking or airflow in most applications. Maximum allowed junction temperature sets the maximum allowed internal power dissipation. Do not allow the maximum junction temperature to exceed 150°C.
Operating junction temperature (TJ) is given by TA + PD × θJA. The total internal power dissipation (PD) is the sum of quiescent power (PDQ) and additional power dissipated in the output stage (PDL) to deliver load power. Quiescent power is the specified no-load supply current times the total supply voltage across the part. PDL depends on the required output signal and load but would, for a grounded resistive load, be at a maximum when the output is fixed at a voltage equal to half of either supply voltage (for equal split-supplies). Under this condition PDL = VS2 / (4 × RL) where RL includes feedback network loading.
The power in the output stage and not into the load that determines internal power dissipation.
As a worst-case example, compute the maximum TJ using an OPA2810-DGK (VSSOP package) configured as a unity gain buffer, operating on ±12-V supplies at an ambient temperature of 25°C and driving a grounded 500-Ω load.
PD = 24 V × 9 mA + 122 /(4 × 500 Ω) = 288 mW
Maximum TJ = 25°C + (0.288 W × 177.2°C/W) = 76°C, which is well below the maximum allowed junction temperature of 150oC.