As mentioned earlier, power dissipation varies in the device, and power estimation is not always accurate or aligned with actual operation. For this reason, an important aspect of in-system thermal analysis is the accurate measurement of the power consumed by the device during testing and operation. The device can measure voltage accurately via the SYSMON circuit. However, current cannot be measured directly from the device. This requires upfront considerations during board design to incorporate a means for measuring the current delivered to the power rails of the device so that actual power can be calculated. Many voltage regulators include telemetry circuitry, though some do not, and others can have compromised accuracy. If current measurement is either not possible or reliable from the regulator, it is advisable to add telemetry to the board to properly characterize power dissipation in the device. Without this crucial information, it becomes difficult to determine whether the thermal management is under-performing or if the system is consuming more power than anticipated.
While current measurement for the device is generally beneficial at any point in a product's lifetime, it is especially important during the prototyping, characterization, and bring-up stages. To balance system cost and debug visibility, some customers choose to incorporate current measurement capabilities into the board, which can be removed after production runs as a cost-saving measure. If the ability to accurately determine power does not exist, it can severely hinder the characterization and debugging of thermal issues.