1. XTR115 + TPS54062
Objective: Increase the available power for sensor and other external circuitry on a remote 2-wire current loop transmitter.
With existing designs, sensors and systems that draw more than ~3.3mA will not be able to meet typical under-scale current or zero-scale levels of 3.8mA or 4mA.
Loop Supply – 16V Desired Iout range = 3.8mA DC – 20.2mA DC with 1mApp HART AC signal Required Sensor Current = 7.1mA

2. XTR115 + TPS54062
Solution: Use low-current buck topology switching power converter to buck down the loop-supply to the required VREG levels. All SMPS current must sink back through IRET of XTR115.

3. XTR115 + TPS54062
Setup:
XTR115 + TPS54062EVM with reduced input capacitance of 1uF
Output: 3.8mA DC + 1mAPP 2.2kHz HART signal
Results:
At 2.2kHz, Max IRET increased to 2.6mA before signal degradation occurred
IRET = 2.6mA
TPS_IOUT = 7.2mA

4. XTR115 + TPS54062
Setup:
XTR115 + TPS54062EVM with reduced input capacitance of 1uF
Output: 3.8mA DC + 1mAPP 2.2kHz HART signal
Results:
Showing the +3.3V output with the reduced 1uF capacitance, output looks good
DC Couple
AC Couple

5. XTR115 + TPS54062
Setup:
XTR115 + TPS54062EVM with reduced input capacitance of 0.47uF
Output: 3.8mA DC + 1mAPP 2.2kHz HART signal
Results:
At 2.2kHz, Max IRET increased to 2.85mA before signal degradation occurred
IRET = 2.8mA
TPS_IOUT = 9mA

6. XTR115 + TPS54062
Setup:
XTR115 + TPS54062EVM with reduced input capacitance of 0.47uF
Output: 3.8mA DC + 1mAPP 2.2kHz HART signal
Results:
At 2.2kHz, Max IRET increased to 2.85mA before signal degradation occurred
IRET = 2.85mA
TPS_IOUT = 9.25mA

7. XTR115 + TPS54062
Setup:
XTR115 + TPS54062EVM with reduced input capacitance of 0.47uF
Output: 3.8mA DC + 1mAPP 2.2kHz HART signal
Results:
At 2.2kHz, Showing distortion with IRET = 2.9mA
IRET = 2.9mA
TPS_IOUT = 9.5mA

8. XTR115 + TPS54062
Setup:
XTR115 + TPS54062EVM with reduced input capacitance of 0.47uF
Output: 3.8mA DC + 1mAPP 2.2kHz HART signal
Results:
At 2.2kHz, Showing distortion with IRET = 3mA
IRET = 3mA
TPS_IOUT = 10mA

9. XTR115 + TPS54062
Setup:
XTR115 + TPS54062EVM with reduced input capacitance of 0.47uF
Output: 3.8mA DC + 1mAPP 2.2kHz HART signal
Results:
Showing the +3.3V output with the reduced 0.47uF capacitance, output looks good
DC Couple
AC Couple

10. XTR115 + TPS54062
Setup:
XTR115 + TPS54062EVM with reduced input capacitance of 0.47uF
Output: 3.8mA DC + 1mAPP 2.2kHz HART signal
Results:
Showing the +16V input ripple with the reduced 0.47uF capacitance, looks similar when compared to original
2.2uF Input cap
0.47uF Input Cap