Low-side bidirectional current sensing circuit with MSP430 smart analog combo



Some MSP430™ microcontrollers (MCUs) contain configurable integrated signal chain elements such as op-amps, DACs and programmable gain stages. These elements make up a peripheral called the smart analog combo (SAC). For information on the different types of SACs and how to leverage their configurable analog signal chain capabilities, visit MSP430 MCUs smart analog combo training. To get started with your design, download the low-side bidirectional current sensing design files. This single-supply low side, bidirectional current sensing solution can accurately detect load currents from –1 A to 1 A. The linear range of the output is from 100 mV to 3.2 V. Low-side current sensing keeps the common-mode voltage near ground and is thus most useful in applications with large bus voltages. This design leverages two of the four integrated op-amp blocks (SACs) in the MSP430FR2355 MCU. One SAC_L3 peripheral is configured as a general purpose op-amp to amplify the voltage across the shunt resistor, while the other is configured as a buffer to provide the bias voltage (Vref). The latter SAC_L3 block can also be configured in DAC buffer mode to provide Vref, replacing the external voltage divider circuit. The output of the circuit can be internally or externally connected to other integrated peripherals in the MSP430FR2355 MCU. For example, the analog-to digital converter (ADC) window comparator can sample this output periodically (with no CPU intervention) and trigger an interrupt when the signal crosses a threshold.
  • Input: I = -1 A to 1 A
  • Output: Vo = 100 mV to 3.2 V
  • Supply:
    • Vcc = 3.3 V
    • Vref = 1.65 V
MSP430 microcontrollers
MSP430FR2311 16-MHz integrated analog microcontroller with 3.75-KB FRAM, OpAmp, TIA, comparator w/DAC, 10-bit ADC MSP430FR2355 24-MHz 105-C integrated analog microcontroller with 32-KB FRAM, Op-Amps/PGAs, 12-bit DACs, 12-bit AD
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* Circuit design Low-side bidirectional current sensing circuit with MSP430™ smart analog combo (Rev. A) PDF | HTML 06 Mar 2020

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