SPRAD53 December 2022 F29H850TU , F29H859TU-Q1 , TMS320F280025C , TMS320F280039C , TMS320F280049C , TMS320F28379D , TMS320F28388D , TMS320F28P650DH , TMS320F28P650DK , TMS320F28P650SH , TMS320F28P650SK , TMS320F28P659DH-Q1 , TMS320F28P659DK-Q1 , TMS320F28P659SH-Q1
In many industrial and automotive applications, an increasingly important requirement is the ability to continually monitor systems and enter appropriate fail-safe states. Particularly in real-time control applications, being able to detect potential faults and perform necessary actions within the system can prevent damage to the system and help support functional safety. This application note describes a technical diagnostic application involving a delta-sigma modulator interfaced with a C2000 microcontroller. The configurable logic block (CLB) peripheral in C2000 real-time MCUs can be utilized for test and measurement applications to provide a greater insight into the status of current and voltage feedback systems making use of delta-sigma modulators.
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Enhanced monitoring and diagnostic features integrated within control systems enable increased system reliability and risk mitigation. In the scheme described within this report, C2000 real-time microcontroller devices' advanced features are used to monitor the status of a delta-sigma modulator. Specifically, the output bistream, which encodes the digital conversion output of an AMC1306x modulator and is connected to a TMS320F28004x MCU for filtering, is monitored to determine if the high-side of the isolated modulator is powered.
The delta-sigma modulator outputs a bitstream of 1s and 0s, where the density of 1s is proportional to the input analog voltage. A differential input signal of 0 V ideally produces a stream of 1s and 0s that are high 50% of the time and low 50% of the time. A large density of 1s corresponds to a greater input voltage. It features additional fail-safe conditions, described in AMC1306 Bitstream & Fail-Safes, which can be used to identify potential problems in the system. For more information about the AMC1306x device, see the AMC1306x Small, High-Precision, Reinforced Isolated Delta-Sigma Modulators With High CMTI Data Sheet.
The configurable logic block on C2000 devices is a peripheral composed of various submodules that assist in performing logic operations independent of the CPU. This peripheral can be used in place of an external FPGA or CPLD to execute complex device logic. The clock and bitstream, which are necessary inputs into the SDFM module when in Mode 0 operation, can be routed to the CLB peripheral purely through software, and CLB can diagnose the output bitstream of delta-sigma modulators. For more information about the TMS320F28004x device, see the TMS320F28004x Data Sheet.
