SLVAF16A March   2021  – December 2021 AFE7920 , AFE7950 , TPS541620 , TPS62912 , TPS62913

 

  1.   Trademarks
  2. 1Introduction and System Description
    1. 1.1 Introduction
      1. 1.1.1 AFE79xx Noise and Ripple Requirements
      2. 1.1.2 TPS62913 Low-Noise and Low-Ripple Buck Converter
      3. 1.1.3 TPS541620 Dual 6A Converter
    2. 1.2 Block Diagram
    3. 1.3 Design Considerations
  3. 2Tests and Results
    1. 2.1 Test Methodology
    2. 2.2 Test Conditions
    3. 2.3 Test Results
  4. 3Schematic
  5. 4Conclusion
  6. 5References
  7. 6Revision History

1.2 Block Diagram

The original AFE7920 RevC evaluation module used a DC-DC converter with LDO followers to provide power to the AFE 1.8 V rails.

GUID-20201202-CA0I-M8CZ-TKNB-42VSFV8NDNXD-low.gif Figure 1-2 Original Power Block Diagram for AFE7920 RevC Evaluation Module

The original EVM power supply is outlined in blue and shown in Figure 1-3. The DC/DC and LDO's consume a large amount of the board area in this design, and uses two sides of the board.

GUID-20210122-CA0I-L5GN-WRWX-KNFNPZVSXWQV-low.gif Figure 1-3 Image of top of Original board with Switchers and LDO's outlined in Blue
GUID-20210122-CA0I-DKZ8-B6W6-9PP4QNRRHRJS-low.gif Figure 1-4 Image of bottom of Original board with Switchers and LDO's outlined in Blue

In the revised design, the LDOs are removed for the 1.8 V rails, and the TPS62913 low-ripple, low-noise DC-DC converter is used instead. This implementation improves the efficiency (reducing power loss), reduces temp rise, and reduces the part count in comparison to a solution using LDOs while maintaining the output voltage ripple and noise requirements of the AFE for good performance.

GUID-20201202-CA0I-HQGN-HPM0-HKR8CFNW77BK-low.gif Figure 1-5 Power Block Diagram for AFE7920 Rev C Evaluation Module with TPS62913

The updated EVM power supply with the TPS62913 and dual output TPS541620 is outlined in blue and shown in Figure 1-7. The DC/DC solution size is considerably smaller in this design, and is on a single side of the board.

Figure 1-6 Image of top of Revised board with TPS541620 and TPS62913 Switchers outlined in Blue
GUID-20210122-CA0I-VBLZ-5HMV-TSBFGTNWNSVP-low.gif Figure 1-7 Image of bottom of Revised board

The schematics for the 1.8 V rails can be found in the Section 3.

Table 1-1 AFE7920 Evaluation Module Component Comparison
Component Original Rev C Rev C with TPS62913
Switching Power Supplies 1 x TPS54824 (3.5mm x 3.5mm) 2 x TPS62913 (2mm x 2mm ea)
LDO's 1 x TPS7A85A 4A LDO (3.5mm x 3.5mm), 1 x TPS7A83A 2A LDO (3.5mm x 3.5mm), 1x TPS7A92 1A LDO (2.5mm x 2.5mm) None
Size of Power Supplies 43 sqmm + passives 8 sqmm + passives