Part Details for TPS3840 by Texas Instruments

This reference design implements Class 0.1 split-phase energy measurement using high-performance: multi-channel analog-to-digital converters (ADC). The independent ADC samples the output of current transformers (CT) at 8 kHz to measure the current and voltage of each leg of the AC mains. The reference design can achieve high accuracy across a wide input current range (0.05 – 100 amps) and supports high sampling frequencies necessary for advanced power quality features such as individual harmonic analysis. Using an independent ADC to sample the CT output provides designers greater flexibility in the choice of metrology microcontrollers when compared to integrated SoCs and dedicated application-specific products. The reference design uses a SimpleLink™ ARM Cortex-M4 host microcontroller to calculate energy measurement parameters.  This design can also use an ADC sample rate of 32 ksps by only enabling a subset of the full energy measurement parameters.

This reference design highlights a versatile use case for a low-power reset IC and a watchdog timer. With less than 1-µA current consumption: the TPS3840 device can be configured to work either as a comparator (with simple 3-pin configuration) or as a universal power supply supervisor that can be daisychained as a sequencer. Additionally: the response and delay time can be configured using an external capacitor. For applications requiring a watchdog operation: the TPS3431 device: a stand-alone programmable watchdog timer with ±2.5% accuracy (typ) can be used.

This reference design showcases non-isolated power supply architectures for protection relays with analog input/output and communication modules generated from 5-: 12-: or 24-V DC input. To generate the power supplies the design uses DC/DC converters with an integrated FET: a power module with an integrated inductor for size- and design-time-constrained applications: a HotRod™ package type for applications requiring low EMI and linear regulators (LDOs) for low ripple. Protections include a flat clamp TVS for input transient protection: an eFuse with configurable load current for overload protection and an ideal diode controller for input reversal protection. Additional features include an auto-switching power MUX: an analog temperature sensor: an input OK indication: a “no load” detection and a voltage supervisor.

This reference design implements Class 0.5 single-phase energy measurement using standalone multi-channel analog-to-digital converters (ADC) to sample a shunt current sensor. With the combination of the shunt sensor and a compact magnetically immune power supply: the design provides protection against magnetic tampering attacks. The design also provides the capability to detect potential tampering from neutral line disconnection. The combination of a high-performance ARM Cortex-M4 MCU to execute the metrology calculations and 8-kHz sampling rate allows the addition of power quality functions: such as individual harmonic analysis.