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

4.1 Measurements with Gated Clock

The TIDA-00466 was programmed so that the FDC2214 was only operating in one of three states: active, sleep, and shutdown. For each state, the current consumption of the device was measured and compared to the expected values given in the data sheet.

Table 2. Current Consumption for Each State: Gated Clock

MEASURED CURRENT (TIDA-00466)
Active Mode 2.78 mA
Sleep Mode 29.7 µA
Shutdown Mode 0.145 µA

These supply current values are taken with a gated external reference clock. If the clock is not turned off while the FDC2214 is in sleep or shutdown mode, the power consumption in these modes will significantly increase as seen in Table 3. The clocking transitions result in an increase of the FDC2214 input pin leakage currents, which is negligible when compared to the normal mode current, but is significant when added onto the lower power mode currents.

Table 3. Current Consumption in Each State Without Gating the External Reference Clock

MEASURED CURRENT (TIDA-00466)
Sleep Mode 271.6 µA
Shutdown Mode 26 µA