Single-supply, low-side, unidirectional 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 single-supply, low-side, unidirectional current-sensing circuit design files. This single-supply, low-side, current sensing solution accurately detects load current up to 1 A and converts it to a voltage between 100 mV and 2.25 V. The circuit uses the MSP430FR2311 SAC_L1 opamp in a noninverting amplifier configuration. There is room for further integration by using the programmable gain stage block within the MSP430FR2355 SAC_L3 peripheral which allows you to integrate the feedback resistor ladder (R2 and R3) into the MCU. The input current range and output voltage range can be scaled as necessary and larger supplies can be used to accommodate larger swings. The output of the second stage op-amp can be sampled directly by the onboard ADC or monitored by the onboard comparator for further processing inside the MCU.
  • Input:
    • I (max) = 1 A
    • V (max) = 250 mV
  • Output: Vo = 100 mV to 2.25 V
  • Supply:
    • Vcc = 3.3 V
    • Vee = 0 V
  • Full-scale range error: FSR = 2.09%
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 Single-supply low-side unidirectional current-sensing circuit with MSP430 SAC (Rev. A) PDF | HTML 06 Mar 2020

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