3.1.5 Power Measurement

The SAMA7D65 Curiosity Pro board features an embedded power measurement device, the PAC1934, which measures the power consumption of the main power rails related to the MPU and peripherals.

The PAC1934 is a four-channel power/energy monitor with a current sensor amplifier and bus voltage monitors that feed high-resolution ADCs. Digital circuitry performs power calculations and energy accumulation. The PAC1934 enables energy monitoring with integration periods from 1 ms to up to 36 hours. Bus voltage, sense resistor voltage, and accumulated proportional power are stored in registers for retrieval by the system master or embedded controller.

Four power rails are monitored: VDD_3V3, VDDIODDR, VDDCORE and VDDCPU. Each rail has a 0.047Ω shunt resistor for current measurement.

Figure 3-9. PAC1934 Power Measurement
Two options are available for retrieving data:
  • Using the on-board USB-to-I²C bridge to access data with an external computer
  • Using the host SAMA7D65 MPU to access the data via a local TWI bus

A set of jumpers is used to manually select between the two access modes on headers J2 and J3.

By default, the USB-to-I²C bridge is selected.

For more details concerning the USB-to-I²C bridge, see USB-to-I²C Bridge (DBGU or On-Board Power Measurement Facility).