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	0010_000	0x20