SBOA569 may 2023 OPA2828
The circuit was simulated to establish the typical relationship between the supply current and internal junction temperature, while the output was driving 1 V over 24.9 Ω. The simulated relationship was found to be linear for both ±5 V and ±15 V supplies.
Since the simulation used a single amplifier, Equation 3 can be restructured to convert the OPA2828's dual supply current to an estimated junction temperature.
This same process can be repeated for simulating the supply current over junction temperature for ±15 V supplies.
Equation 5 was restructured to work for the OPA2828's supply current.
Next, the supply current was measured over a range of ambient temperatures and converted into the respective internal junction temperature.
In the ±5 V supplies case, both package types heated up at a fairly uniform rate as ambient temperature increased. The HVSSOP package ranged from about 70 °C to 120 °C, while the typical package ranged from 85 °C to 130 °C.
In the ±15 V supplies case, the difference between the two package temperature remained uniform. The HVSSOP package ranged from 100 °C to 145 °C, while the typical package ranged from 145 °C to 185 °C. The temperature delta for both the ±5 V and ±15 V supplies cases were plotted in Figure 3-5.
As observed above, the ±5 V supplies case had an average of 14.3 °C temperature increase from the HVSSOP to the typical SOIC package, while the ±15 V case was an average of 39.8 °C temperature increase. This can be used to estimate the difference in input offset voltage drift and input bias current between the two packages. The OPA2828 has a typical offset voltage drift of ±0.3 uV/°C and a maximum drift of ±1.3 uV/°C. A theoretical input bias current drift of 30 pA/°C was used for comparisons.
Characteristic | Error Increase (Supply Voltages = ±5 V) | Error Increase (Supply Voltages = ±15 V) |
---|---|---|
Typical Offset Voltage | ±4.29 uV | ±11.94 uV |
Maximum Offset Voltage | ±18.59 uV | ±51.74 uV |
Input Bias Current | ±429 pA | ±1194 pA |
By using the average temperature increases, the estimated Θja difference between the HVSSOP and the typical package is 48.1 °C/W. This is lower than the earlier estimations which can be attributed to physical differences between the modified HVSSOP and SOIC packages. The accuracy benefits seen in Table 3-1 show the importance of using a thermally-enhanced package in high precision applications.