3 Bench Test Results

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.

Figure 3-1 ±5 V Supplies, Supply Current vs Temperature Simulation

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.

Figure 3-2 ±15 V Supplies, Supply Current vs Temperature Simulation

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.

Figure 3-3 ±5 V Supplies, Junction vs Ambient 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.

Note: The OPA2828 features a thermal shutdown mode when the internal temperature reaches approximately 180 °C, this was measured and verified with the device being tested. The output is disabled until the internal temperature cools down to 160 °C, at which point the output resumes. The OPA2828's output is only guaranteed to be reliable up to 150 °C which is surpassed in the above situation. More information about thermal considerations is located in section 8.4.1.1 of the data sheet.

Figure 3-4 ±15 V Supplies, Junction vs Ambient Temperature

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.

Figure 3-5 Temperature Delta from HVSSOP to Typical Package

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.

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.