3.1.5 Power Measurement

One Microchip DC power/energy monitor is embedded on the SAMA7G54-EK board and provides a four-channel current sense monitoring ensured by the PAC1934 device.

The device communicates with the MPU via a Two-Wire Interface (TWI) and an alert output signal.

The PAC1934 is a four-channel power/energy monitor with current sensor amplifier and bus voltage monitors that feed high resolution ADCs. A digital circuitry performs power calculations and energy accumulation. The PAC1934 enables energy monitoring with integration periods ranging from 1 ms to 36 hours. Bus voltage, sense resistor voltage, and accumulated proportional power are stored in registers for retrieval by the system host or embedded controller. For more information about the PAC1934, refer to the product web page.

Four current sense resistors are populated on board for measuring voltage and current consumption on the power rails:

  • 10 mΩ on VDD_3V3 node—3.3V power rail power consumtion on SAMA7G5
  • 10 mΩ on VDDIODDR node—1.35V power rail power consumption on SAMA7G5 DDR I/Os and on DDR3L memory
  • 10 mΩ on VDDCORE node—1.1V power rail power consumption on SAMA7G5 core
  • 10 mΩ on VDDCPU node—1.275V power rail power consumption on SAMA7G5 CPU
Figure 3-8. PAC1934 Power Measurement Schematic
Table 3-2. PAC1934 Signal Descriptions
PIO Signal Name Shared PIO Signal Description
PC10 PAC1934_TWCK PMIC TWI clock signal
PC9 PAC1934_TWD PMIC TWI data signal
PC8 PAC1935_INT_PC8 – PAC1934 interrupt
Table 3-3. PAC1934 TWI Address
Device 7-bit Client Address Full Address with RD/WR#
PAC1934 TWI Read 0010_000 0x21
PAC1934 TWI Write 0x20