SONOMA (MAXREFDES14#): Isolated Power Measurement Subsystem Reference Design

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AC measurement applications often require electrical isolation to protect the system and user from high voltages. Galvanic isolation is often achieved by using bulky sensor voltage/current transformers or by isolating the data and power interfaces from the measurement subsystem. However, these approaches take up considerable space, have hidden costs and design challenges.

The Sonoma (MAXREFDES14#) power measurement subsystem reference design utilizes a single pulse transformer to achieve electrical isolation from the system and uses a resistor as the sensing element. The result is a small, cost-effective circuit board.

The Sonoma design features an isolated power measurement processor ( MAX78615+LMU) ; a multi-channel, high-precision analog-to-digital converter (ADC) ( MAX78700 ); a pulse transformer; an optional 20MHz crystal; and the ability to convert AC voltage and current into a Detection resistor for measuring signal. Featuring embedded load monitoring unit (LMU) firmware, non-volatile memory for calibration and configuration data, Sonoma is a complete measurement subsystem that can be integrated into any design.

Figure 1. Sonoma subsystem design block diagram.

Competitive Advantage

• Built-in non-volatile memory for calibration and configuration parameters

• Complete electrical isolation using a single transformer

• Small circuit board size

• Low BOM cost