The MAXREFDES77# peripheral module provides the necessary hardware to interface the MAX44285 dual-channel high-side current-sense amplifier device to any system that utilizes Pmod™-compatible expansion ports configurable for SPI communication. The IC features an input common-mode voltage range from 2.7V to 76V with 80kHz small-signal bandwidth, making it ideal for interfacing with a SAR ADC for multichannel, multiplexed data acquisition systems.
Refer to the MAX44285 IC data sheet for detailed information regarding operation of the IC and the USB2PMB1# (Munich) adapter board data sheet for detailed information regarding the Munich board and GUI.
The MAXREFDES77# peripheral module can plug directly into a Pmod-compatible port (configured for SPI) through connector X1. For information on the SPI protocol, refer to the MAX11125 IC data sheet.
Connector X1 provides connection of the module to the Pmod host. See Table 1 for detailed description.
Connectors X3 and X4 provide connection to external power and the system loads.
The MAXREFDES77# peripheral module contains the MAX6126A30+ voltage reference to provide 3.0V reference to the ADC MAX11125.
The MAXREFDES77# peripheral module also contains a temperature sensor, MAX6607IXK+, to measure the external temperature.
The Munich GUI is available for download and is provided to facilitate the evaluation of the MAXREFDES77#. Refer to the Munich GUI Quick Start Guide document for further details.
Table 1. Connector X1 (SPI Communication)
|1||SPI_CS||Chip Select. Assert low to enable the SPI interface.|
|3||SPI_MOSI||MAX44285 Serial Data Input|
|4||Active-Low CONVST||ADC Conversion Control Input. Assert low to initiate an ADC conversion.|
|5||SPI_MISO||MAX44285 Serial Data Output|
|6||Active-Low EOC||End of Conversion Output. Data is valid after active-low EOC pulls low.|
|7||SPI_SCLK||MAX44285 Serial Clock Input|
|11, 12||+3.3V||+3.3V Power Supply|
The MAXREFDES77# allows measuring supply-voltage (up to 65V) and supply-current (up to 26A) for 2 different loads with independent supplies.
Figure 1. MAXREFDES77# connected to Munich board.
Figure 2. MAXREFDES77#/Munich GUI.
Volt per LSB = 60V/(ADCcounts at 60V - ADCcounts at 0V)
For accurate calibration, use load with current at ~75% of the range.
A per LSB = 20A/(ADCcounts at 20A - ADCcounts at 0A)
The Munich GUI automatically saves these calibration settings once the calibration menu is closed. Therefore, if the same hardware is used, it is not neccesarry to re-calibrate.
Figure 3. Calibration menu.
The MAXREFDES77# reference design was verified and tested under full input range and different output load conditions, and the results were captured by Munich GUI as shown in Figure 4.
Figure 4. MAXREFDES77# lab measurements.
Pmod is a trademark of Digilent Inc.