More information on the current and voltage sensors, ADCs, and other hardware is provided in the
following sections.
Figure 2 shows a block diagram of the high-level interface that is used for a single-phase energy meter
application using the F6736(A). A single-phase two-wire star connection to the mains is shown with
tamper detection. Current sensors are connected to each of the current channels, and a simple voltage
divider is used to measure the corresponding voltages. The CT has an associated burden resistor that
must be connected at all times to protect the measuring device. The choice of the CT and the burden
resistor is done based on the manufacturer and current range required for energy measurements. The
choice of the shunt resistor value is determined by the current range, gain settings of the SD24, and the
power dissipation at the sensors. The voltage divider resistors for the voltage channel are selected to
make sure that the mains voltage is divided down to the normal input ranges that are valid for the
MSP430™ SD24. For these values, see the MSP430x5xx and MSP430x6xx Family User's Guide
(SLAU208) and the device-specific data sheet (SLAS731 for the MSP430F6736 and SLASE46 for the
MSP430F6736A)