Teridian smart power meter IC family offers alternative to current transformers

Utility power meters often must rely on a current transformer for polyphase applications: Current transformers have drawbacks: They are relatively expensive, require additional copper wiring, and can be tampered with by the use of a large permanent magnet. A shunt current sensor is often a simpler and less expensive solution, but only works for single phase, single element systems: Voltages measured across phases are too high for the subsequent electronics and also for maintenance personnel. (For more on sensors for smart meters, see, Tamper-resistant smart power meters rely on isolated sensors.)

AFE = analog front end; PGA = programmable gain amplification

Teridian’s new SOC smart metering product family, which includes the 71M6541x and 71M6xx1, features digitally isolated current sensors based on the company’s proprietary MicroDAAisolation technology. The new 71M6541x is a stand-alone meter system-on-chip (SOC) for single-phase systems. For multi-phase systems, designers can eliminate the need for a  current transformer by using an inexpensive pulse transformer to interface the 71M6541x to the 71M6xx1 isolated sensor IC, which then connects to a current-sensing shunt element. The signal that the 6541 sends to the pulse transformer provides a communication signal and has enough power to energize the sensor IC, eliminating the needs for a current transformer and associated copper wiring in 2-phase residential meters, with up to ANSI 200A class 0.2 accuracy. 

Pricing info: “The 71M6541x is offered in 64-pin LQFP packages with 32KB or 64KB Flash options and prices starting at $2.00 at 10,000 quantities.  The 71M6xx1 isolated sensors are offered in 8-pin SOIC packages with prices starting at $1.50 for 10,000 quantities, which varies depending on current and accuracy range.”