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

6.1 Estimating Current Consumption

The following procedure can be used to estimate the current consumption of the FDC2x1x . First, the active time, or time the device spends in normal mode, should be determined. As expressed in Equation 1, this includes the sensor startup time, tS, the sensor conversion time, tC, and the data readback time, tRB. The channel switch delay time, tSD, can be ignored while operating in single channel mode. Once tN has been calculated, the percentage of time the device spends in active mode, DN, can be calculated using Equation 7 where TS is the sampling period. The percentage of time the device spends in sleep mode, DS, can also be calculated by using Equation 8.

Equation 7. eq05_snoa943.gif
Equation 8. eq06_snoa943.gif

Equation 9 then estimates the amount of power the FDC2x1x will burn given the above percentages per period (DN and DS) where IN is the supply current in active mode and IS is the supply current in sleep mode (given in Table 2).

Equation 9. eq07_snoa943.gif