SWRA577A October   2017  – November 2020 AWR1243 , AWR1443 , AWR1642 , AWR1843 , AWR1843AOP , AWR2243 , AWR6843 , IWR1443 , IWR1642 , IWR1843 , IWR6443 , IWR6843 , IWR6843AOP , LP87524B-Q1 , LP87524J-Q1

 

  1.   Trademarks
  2. 1Introduction
  3. 2Power Supply Ripple and Noise Specifications
  4. 3Reference Solution
  5. 4Low Cost LC Filter Solution
    1. 4.1 LDO vs LC Filter Scheme Comparison
      1. 4.1.1 Waveguide Loopback Tests
      2. 4.1.2 Spur/Noise Floor Level
      3. 4.1.3 Voltage Transient Behavior
    2. 4.2 System Tests
      1. 4.2.1 Sensor Configuration
      2. 4.2.2 System Test With Static Object
      3. 4.2.3 Spur/Noise Floor Level
  6. 5Summary

4 Low Cost LC Filter Solution

For the cost sensitive use cases, a low cost LC filter (Ferrite bead + Device Decoupling capacitor) based solution could be used, which would effectively replace the LDOs on the 1.8 V and 1.0 V rails. This approach would have performance and the system level trade-off.

Figure 4-1 shows the Power management scheme.

GUID-243D018C-B15A-4A5F-A0BD-D7A939C9755D-low.pngFigure 4-1 Power Management Scheme With LC filter
Note:

The capacitors shown above in the LC filter are the device decoupling capacitors.

The recommended Ferrite bead components are shown in Table 4-1.

Table 4-1 Recommended Ferrite Bead Components
LC FilterInductor Value (µH)DC Resistance (mΩ)Impedance @ 100 MHz (Ω)Size (inches)Pole Frequencies w.r.t. 1V Rail Decaps/1.8V Rail Decaps (KHz)DC Current (A)Theoretical Rejection Offered by the Filter (dB)Manufacturer Part Number
Ferrite Bead0.1909251200603113.9364BLM18KG121TH1