MSP430I2020: Clarification on Neutral & Ground Interface

REDDY Y

Part Number: MSP430I2020

Hi TI team,
This is regrading Single Phase Energy Meter Design with RS-485 communication.
We are planning to use MSP430I2020 Metering MCU for the same.

I need your support in reviewing the neutral connection & Ground portion wrt MCU ADC.

Pls review with the below notes..

Note 1: There is a bridge rectifier in between Neutral_IN & GND (So Metering MCU GND & Neutral are same)

Note 2 : AGND & GND are short

Is that ok if Neutral & AGND/GND are diffreent ??
If not OK, pls suggest the power supply ckt.

1PH Energy meter_SM.pdf

over 2 years ago

0 Thomas Foxcroft over 2 years ago

Expert 2996 points

Reddy Y:

I would like to make one comment.

Your schematics show that the neutral conductor from high powered AC is connected with AVSS and DVSS on the MSP430. I would not have the microcontroller's VSS connected directly with the AC neutral. Here's why: although the AC neutral conductor and the microcontroller's VSS can be viewed as grounds, the neutral conductor may not always have the same strict voltage potential that is required by the microcontroller, so they should be [galvanically] isolated.

See SLYY204, "Addressing high-voltage design challenges with reliable and affordable isolation technologies," for an elaboration on what I said.

0 REDDY Y over 2 years ago in reply to Thomas Foxcroft

Intellectual 880 points

Hi Thomas

as per Metering application notes (TIDRDN0, SLAA638) Neutral shall be conencted to AVSS & DVSS.
Isolated solution is very expensive for the Energy Meter applcation as product is cost sensitive.

My doubt is can I have bridge rectifier diodes in between (Neutral input and AVSS/DVSS) or not ??

0 Jace H over 2 years ago in reply to REDDY Y

TI__Guru 56685 points

Hello Reddy,

Please see the following application note for MSP430I20xx recommendations.
Implementation of One- or Two-Phase Electronic Watt‑Hour Meter Using MSP430i20xx

0 REDDY Y over 2 years ago in reply to Jace H

Intellectual 880 points

The above mentioned application note doesn't have info related to bridge rectifier.

Kindly clarify..

My doubt is can I have bridge rectifier diodes in between (Neutral input and AVSS/DVSS) or not ??

0 Jace H over 2 years ago in reply to REDDY Y

TI__Guru 56685 points

Hello Reddy,

I am unable to comment about your specific inquiry as it is outside my scope. What I can do is point you to collateral we have on the subject of utilizing MSP430I20xx devices in energy metering/monitoring spaces in the hope that it helps you further your design. Please see not only the application note I linked above, but the following ones as well.

Single Phase and DC Embedded Metering (Power Monitor) Using MSP430I2040

Single-Phase AC and DC Power Monitor with Wire Resistance and EMI Capacitor Compensation

TI Designs Three-Outlet Smart Power Strip

0 REDDY Y over 2 years ago in reply to Jace H

Intellectual 880 points

My question is related to ADC & GND connections for MSP430I2040.
pls let me know whom to approach for this clarification ???

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MSP430I2020: Clarification on Neutral & Ground Interface