SNOA943 January   2016 FDC2112 , FDC2112-Q1 , FDC2114 , FDC2114-Q1 , FDC2212 , FDC2212-Q1 , FDC2214 , FDC2214-Q1

 

  1.   Power Reduction Techniques for the FDC2214/2212/2114/2112 in Capacitive Sensing Applications
    1.     Trademarks
    2. 1 Duty-Cycling
      1. 1.1 FDC2x1x Operational Parameters That Affect Duty Cycling
    3. 2 Clock Gating
    4. 3 Test Setup
    5. 4 Measurement Results
      1. 4.1 Measurements with Gated Clock
    6. 5 Current Consumption Measurements vs Data Conversion Time
      1. 5.1 Data Readback Overhead
    7. 6 Comparison of Measured and Estimated Current Consumption
      1. 6.1 Estimating Current Consumption
    8. 7 Results
    9. 8 Summary

3 Test Setup

Duty-cycling the FDC2x1x was tested on the Noise-immune Capacitive Proximity Sensor System Reference Design (TIDA-00466) with only one channel (Channel 0, proximity sensor) enabled. The current flowing through the FDC2214 was measured using a digital multi-meter. The test setup is shown in Figure 4 and the testing conditions are given in Figure 4.

test_setup_snoa943.gifFigure 4. Test Setup

Table 1. Testing Conditions

CHANNEL 0
Reference Frequency (MHz) 40
Sensor Frequency (MHz) 5.3
Amplitude (V_PP) 1.22
SETTLECOUNT 30
Current Drive Setting (mA) 0.069

The reference frequency was set by an external crystal oscillator and the current drive was set to achieve the recommended voltage amplitude for the oscillation waveform, which is between 1.2 and 1.8 VPP.