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MSP430AFE253: ADC Design and Differential Channel Grounding Issues

Part Number: MSP430AFE253

Hi team,

Here's an issue from the customer may need your help:

This customer wants to design a DC electrical energy power meter, the voltage is 1000V, and the current is tentatively 1000A. The voltage adopts a voltage divider resistor, and the current adopts a 75mv shunt resistor FL-2.

The design refers to the design of the official AC energy meter, and the customer has several questions.

The picture below is a schematic diagram of the customer's design:

customer design


The pictures below are from TI DEMOs:









1.Why the series resistance of VIN_P channel is 100R, and the other channels are 1K? This is the case with many official DEMOs.

2.AGND is grounded, why should VIN_M be grounded? Is each channel grounded? Is the grounding because of any requirements for discharging current?

3.The sampling resistor is usually connected in Kelvin connections. If R24 and R25 (R26 are reserved) are grounded according to the picture-1, will the Kelvin connection be destroyed? Although "High voltage negative electrode" and "current-" are theoretically short-circuited, "current-" is to be connected to the special contact of the shunt. Is it ok to keep only one R24 grounding in the circuit?


Best Regards,

Yale Li

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