SLUA748A December   2015  – April 2016 BQ25120 , BQ51003 , TPS61046 , TPS61240 , TPS62743

 

  1.   Trademarks
  2.   Power Management Reference Design for a Wearable Device with Wireless Charging Using the bq51003 and bq25120
    1. 1 Wearable Power Design
      1. 1.1 Wireless Charging Input
      2. 1.2 Battery Charger, MCU, Radio, and Sensor Power
      3. 1.3 Second Buck Output for MCU, Radio or Sensor
    2. 2 PMOLED Display Power Design
    3. 3 Heart Rate Monitor or e-Ink Power Design
    4. 4 Layout Guidelines for Wearable Design
      1. 4.1 Wireless Receiver (bq51003)
      2. 4.2 Linear Charger (bq25120)
      3. 4.3 Buck Converter (TPS62743/6)
      4. 4.4 Boost Converters (TPS61046 and TPS61240)
      5. 4.5 General Considerations
    5. 5 References
  3. AExperimental Results
    1. A.1 Experimental Results
  4.   Revision History

A.1 Experimental Results

Efficiency of Wireless Input Stage. The figure shows the efficiency across the power range with the bq51003. This is the total DC/DC system efficiency including the transmitter, coils and receiver. Testing was done with the TIDA-00334 Small Form Factor Transmitter reference design (5-V input) and the TDK WR222230-26M8-G coil. The TIDA-00334 reference design is pictured below with the results.

tida-00334_board.pngFigure 13. TIDA-00334 Board
D001_SLUA748.gifFigure 14. Wireless Power Efficiency

Figure 15 and Figure 16 show the efficiency and load regulation of the bq25120 1.8V buck output with a 3.8V VBAT input. For full performance data of the BQ25120, see the datasheet.

D002_SLUA748.gifFigure 15. BQ25120 Buck Efficiency

D003_SLUA748.gifFigure 16. BQ25120 Buck Load Regulation

Figure 17 and Figure 18 show the efficiency and load regulation of the TPS62743 1.8 V Buck Output from a 3.8V VBAT input. The input to the TPS62743 is connected to PMID, so the efficiency includes the drop through the bq25120 battery discharge FET. For full performance data of the TPS62743, see the datasheet.

D004_SLUA748.gifFigure 17. TPS62743 Buck Efficiency

D005_SLUA748.gifFigure 18. TPS62743 Buck Load Regulation

Figure 19 and Figure 20 show the efficiency and load regulation of the TPS61046 12 V Boost Output from a 3.8V VBAT input. The input to the TPS61046 is connected to PMID, so the efficiency includes the drop through the bq25120 battery discharge FET. For full performance data of the TPS61046, see the datasheet.

D006_SLUA748.gifFigure 19. TPS61046 Boost Efficiency

D007_SLUA748.gifFigure 20. TPS61046 Boost Load Regulation

Figure 21 and Figure 22 show the efficiency and load regulation of the TPS61240 5 V Boost Output from a 3.8V VBAT input. The input to the TPS61240 is connected to PMID, so the efficiency includes the drop through the bq25120 battery discharge FET. For full performance data of the TPS61240, see the datasheet.

D008_SLUA748.gifFigure 21. TPS61240 Boost Efficiency

D009_SLUA748.gifFigure 22. TPS61240 Boost Load Regulation

The following thermal images are of the board with various outputs and loads applied.

Table 2. Board Outputs and Loads

BQ25120 SYS BQ25120 LS/LDO TPS61046 BOOST 12V TPS61240 BOOST 5V TPS62743 V_BUCK CURRENT FROM VBAT (A) (1) BOARD MAX TEMP °C (2) BQ25120 MAX TEMP °C AMBIENT TEMP °C
Image 1 200 mA 0 mA 0 mA 0 mA 0 mA 0.11117 27.08 25.28 22.5
Image 2 200 mA 100 mA 0 mA 0 mA 0 mA 0.20982 28.08 26.58 22.5
Image 3 200 mA 100 mA 100 mA 0 mA 0 mA 0.67541 57.72 37.95 22.5
Image 4 200 mA 100 mA 100 mA 200 mA 0 mA 1.0723 69.2 53.51 22.5
Image 5 200 mA 100 mA 100 mA 200 mA 200 mA 1.19482 80.79 64.66 22.5
Image 6 0 mA 0 mA 0 mA 0 mA 0 mA 0.000041 24.47 23.29 22.5
image1_slua748.pngFigure 23. Image 1
image2_slua748.pngFigure 24. Image 2
image3_slua748.pngFigure 25. Image 3
image4_slua748.pngFigure 26. Image 4
image5_slua748.pngFigure 27. Image 5
image6_slua748.pngFigure 28. Image 6

Table 3. Board Outputs and Loads

BQ51003 BQ25120 SYS BQ25120 LS/LDO TPS61046 BOOST 12 V TPS61240 BOOST 5 V TPS62743 V_BUCK (1) BQ25120 MAX TEMP °C (2) BQ51003 MAX TEMP °C AMBIENT TEMP °C
Image 7 On 100 mA Fast Charge Off Off Off Off 31.7 32.18 22.5
Image 8 On 200 mA Fast Charge Off Off Off Off 39.66 34.31 22.5
Image 9 On 300 mA Fast Charge Off Off Off Off 35.13 38.52 22.5
image7_slua748.pngFigure 29. Image 7
image8_slua748.pngFigure 30. Image 8
image9_slua748.pngFigure 31. Image 9