SNOA949 May   2016 LDC1312 , LDC1312-Q1 , LDC1314 , LDC1314-Q1 , LDC1612 , LDC1612-Q1 , LDC1614 , LDC1614-Q1

 

  1.   Power Reduction Techniques for the Multichannel LDCs in Inductive Sensing Applications
    1.     Trademarks
    2. 1 Introduction
    3. 2 Duty Cycling
      1. 2.1 Operational Parameters That Affect Duty Cycling
    4. 3 Clock Gating
    5. 4 Test Setup
    6. 5 Measurement Results
      1. 5.1 Measurements with Internal Clock
      2. 5.2 Current Consumption Measurements vs Data Conversion Time
        1. 5.2.1 Data Readback Overhead
        2. 5.2.2 Comparison of Measured and Estimated Current Consumption
          1. 5.2.2.1 Estimating Current Consumption
        3. 5.2.3 Results
    7. 6 Summary

5.2.1 Data Readback Overhead

The LDC1614 does not retain its conversion results when in sleep mode. Because of this, the device cannot be put into the sleep state until the channel conversion measurements have been read by the microcontroller. Therefore, the data registers must be read while the device is still running in active mode, which results in a fixed power consumption overhead. From the data given in Table 3, the data readback time is 0.688 ms if a 400-kHz I2C interface is used. This overhead has a greater percentage impact on conversion times at low RCOUNT values where the data conversion times are less than 10x the data readback time.

Table 3. The Effect of Data Readback Overhead on Device Active Time

RCOUNT Data Conversion Time
(tS+ tC + tSD) (ms) 		Readback Time
(tRB) (ms) 		Data Conversion Time +
Data Readback Time (ms)
500 0.196 0.688 0.884
1000 0.381 0.688 1.069
5000 1.855 0.688 2.543
10000 3.699 0.688 4.387
20000 7.385 0.688 8.073
30000 11.072 0.688 11.76
40000 14.758 0.688 15.446
50000 18.445 0.688 19.133