LOOP POWERED TRANSMITTER WITH A SINGLE TAP DATA ISOLATION TRANSFORMER AND UNIPOLAR VOLTAGE CONVERTERS

• US 20150236759A1
• Filed: 02/19/2015
• Published: 08/20/2015
• Est. Priority Date: 02/19/2014
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: CORNELL, Evan David, TRACY, Christopher Sean, SINGH, Ajinder Pal
• Granted Patent: US 9,544,027 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H04B 5/266 One coil at each side, e.g. with primary and secondary coils
• CPC Class Codes: H04B 5/72 for local intradevice communication
• CPC Class Codes: H04B 5/75 for isolation purposes

Abstract

A loop-powered transmitter includes a data isolation transformer including primary and secondary windings and an analog-to-digital converter (ADC) to convert a sensor signal to a digital value. The transmitter also includes a first microcontroller coupled between a multi-signal interface of the ADC and only one tap of the primary winding of the data isolation transformer, and a second microcontroller coupled to the secondary winding of the data isolation transformer. The first microcontroller is configured to receive the digital value from the ADC over the multi-signal interface and to provide data indicative of the digital value via a single output data line through the tap of the primary winding of the data isolation transformer to the second microcontroller. Unipolar voltage converters may also be included in the transmitter along with a current limiting resistor for the data isolation transformer to reduce the risk of saturating the data isolation transformer.

Claims

1. A loop-powered transmitter, comprising:

a data isolation transformer including a primary winding and a secondary winding;

an analog-to-digital converter (ADC) to convert a sensor signal to a digital value, the ADC including a multi-signal interface; and

a first microcontroller coupled between the multi-signal interface of the ADC and only one tap of the primary winding of the data isolation transformer;

wherein the first microcontroller is configured to receive the digital value from the ADC over the multi-signal interface and to provide data indicative of the digital value via a single output data line through the tap of the primary winding of the data isolation transformer.

2. The loop-powered transmitter of claim 1 further comprising:

a power isolation transformer having a primary winding and a secondary winding;

a first unipolar voltage converter coupled to the secondary winding of the power isolation transformer to thereby receive power through the power isolation transformer and to generate a unipolar operating power to operate the ADC and the first microcontroller; and

a current limiting resistor connecting the primary winding of the data isolation transformer to ground to thereby prevent the primary winding of the data isolation transformer from saturating.

3. The loop-powered transmitter of claim 2 further comprising a second microcontroller coupled to the secondary winding of the data isolation transformer and configured to receive the digital value from the first microcontroller through the data isolation transformer.

4. The loop-powered transmitter of claim 3 further comprising:

a digital-to-analog converter (DAC) coupled to the second microcontroller; and

a second unipolar voltage converter coupled to the primary winding of the power isolation transformer and, from a voltage on a current loop, to generate a unipolar operating power to operate the second microcontroller and the DAC.

5. The loop-powered transmitter of claim 4 wherein the second microcontroller couples to the DAC via a multi-signal interface.

6. The loop-powered transmitter of claim 1 further comprising:

a power isolation transformer having a primary winding and a secondary winding;

a second microcontroller coupled to the secondary winding of the data isolation transformer; and

a unipolar voltage converter coupled to the primary winding of the power isolation transformer to generate a unipolar operating power from a current loop, the generated unipolar operating power to operate the second microcontroller.

7. The loop-powered transmitter of claim 6 further comprising a current limiting resistor connecting the primary winding of the data isolation transformer to ground.

8. The loop-powered transmitter of claim 1 further including a current limiting resistor connecting the primary winding of the data isolation transformer to ground to thereby prevent the primary winding of the data isolation transformer from saturating.

9. A loop-powered transmitter, comprising:

a power isolation transformer;

a data isolation transformer including a primary winding and a secondary winding;

an analog-to-digital converter (ADC) configured to convert an analog signal to a digital value and to provide the digital value through the data isolation transformer;

a first unipolar voltage converter to receive power through the power isolation transformer and to generate a unipolar operating power to operate the ADC; and

a current limiting resistor connecting the primary winding of the data isolation transformer to ground to thereby prevent the primary winding of the data isolation transformer from saturating.

10. The loop-powered transmitter of claim 9 further comprising a microcontroller coupled between only one tap of the secondary winding of the data isolation transformer and a digital-to-analog converter (DAC), wherein the microcontroller couples to the DAC via a multi-signal interface.

11. The loop-powered transmitter of claim 9 further comprising first and second microcontrollers and a digital-to-analog converter (DAC), wherein the ADC is configured to provide the digital value through the first and second microcontrollers and the data isolation transformer to the DAC.

12. The loop-powered transmitter of claim 11 wherein the first microcontroller is coupled between a multi-signal output interface of the ADC and only one tap of a primary winding of the data isolation transformer, and the second microcontroller is coupled between the secondary winding of the data isolation transformer and the DAC.

13. The loop-powered transmitter of claim 11 further comprising a second unipolar voltage converter coupled to a primary winding of the power isolation transformer and is configured to generate, from a voltage on a current loop, a unipolar operating power to operate the second microcontroller and the DAC and to provide power to the first unipolar voltage converter through the power isolation transformer.

14. The loop-powered transmitter of claim 13 wherein the DAC is configured to modulate a current on the current loop based on the digital value received by the second microcontroller through the data isolation transformer from the first microcontroller.

15. The loop-powered transmitter of claim 9 wherein the analog signal includes a sensor signal.

16. The loop-powered transmitter of claim 9 wherein the analog signal includes a temperature sensor signal.

17. A loop-powered transmitter system, comprising:

a first unipolar voltage converter;

a second unipolar voltage converter;

a power isolation transformer including a primary winding and a secondary winding, the primary winding of the power isolation transformer coupled to the second unipolar voltage converter and the secondary winding of the power transformer coupled to the first unipolar voltage converter;

a data isolation transformer including a primary winding and a secondary winding;

an analog-to-digital converter (ADC) providing a multi-signal interface;

a first microcontroller coupled between the multi-signal output interface of the ADC and only a single tap of the primary winding of the data isolation transformer;

a second microcontroller coupled to only a single tap of the secondary winding of the data isolation transformer;

wherein the first microcontroller is configured to receive a digital value from the ADC over the multi-signal interface and to provide data indicative of the digital value via a single output data line through the tap of the primary winding of the data isolation transformer to the second microcontroller;

wherein the ADC and the first microcontroller are configured to receive unipolar operating power from the first unipolar voltage converter, and the second microcontroller is configured to receive unipolar operating power from the second unipolar voltage converter; and

a current limiting resistor connecting the primary winding of the data isolation transformer to ground to thereby prevent the primary winding of the data isolation transformer from saturating.

18. The loop-powered transmitter system of claim 17 further including a sensor providing a sensor signal to the ADC.

19. The loop-powered transmitter system of claim 17 further including a temperature sensor providing a sensor signal to the ADC.

20. The loop-powered transmitter system of claim 17 further comprising a digital-to-analog converter (DAC) that couples to the second microcontroller via a multi-signal interface