The power measurement board includes eight measurement channels which support for eight programmable gain amplifiers(LTC6915) and two ADC converters(AD7175). The measurement board measures the voltage drop across sampling resistor, and send to the ADC after the voltage drop is processed by amplifier and make it available via SPI. Microcontroller LPC55S69 collects the data from the measurement circuit and send it to the host computer via USB VCOM port. The MCU can control the gain value of programmable gain amplifiers by SPI when different power circuit are measured.
The host computer connects to the power measurement board through the USB virtual serial port, the MCU initializes and configures the measurement unit by SPI, and starts to measure the inside current and monitor the voltage. MCU adjust the gain parameter and then transmit current and voltage data to MCU by SPI, then MCU transmits the data to the host computer for processing and display through the virtual serial port. The voltage drop of the measured circuit to be measured is firstly amplified by the programmable amplifier LTC6915, and MCU monitor the state which whether the data is abnormal at the same time.
R0 is the sampling resistor, LTC6915 is a selectable programmable amplifier, the gain can be set to 14 kinds, PGA gain parameter is adjusted when the current changes. ADC7175 is the 24-bit high-precision ADC, which is more advantageous in the application of small current measurement. When the MCU switches the low power mode to the normal mode, and the LTC6915 will reduce the gain value by SPI.
The power measurement board provides easy connection method by two-wires cable. For example, the MIMXRT1180EVK and MIMXRT1020EVK are connected with power measurement board.
The USB virtual COM is used for data transfer, and display by PMT(power management tool) or other PC GUI, the measurement power data include current, voltage and power.
There are more detailed descriptions in the attachment.
