SLVAF41A March   2021  – November 2021 TPS61094


  1.   Trademarks
  2. 1Introduction of the Smart Meter
  3. 2The Traditional Power Solution of the Smart Meter
    1. 2.1 Connecting the Battery Directly
    2. 2.2 The Pure Boost TPS61094 or TPS610995 Solution
  4. 3The TPS61094 with Supercap Solution
    1. 3.1 TPS61094 Description
    2. 3.2 System Operation Description
  5. 4Solution Comparison
  6. 5Supercap Behavior and Design
    1. 5.1 Supercap Life Time
    2. 5.2 Supercap Leakage Currrent
    3. 5.3 Supercap Parameter Design in TPS61094 Solution
  7. 6Test Report Based on TPS61094 Solution
    1. 6.1 Test Waveform
      1. 6.1.1 NB-IoT Data Transmission
      2. 6.1.2 Supercap Charging
    2. 6.2 Efficiency
  8. 7References
  9. 8Revision History

Supercap Parameter Design in TPS61094 Solution

Because the supercap lifetime and leakage current are strongly related to working voltage, TI suggests to set supercap charging terminal voltage to 2 V, which could achieve 20 years life time at 65 ℃ and the leakage current is about 18% of the datasheet spec.

The capacity of the supercap depends on Rx/Tx transmission loss. Let's take NB-IoT as the example. Assume the transmission internal is 24 h that is once data exchange every day, 3.3 V supply voltage, and a payload of 200 Bytes. The power consumption of one transmission is about 4 J. To leave 20 % margin, the target storage energy is set as 4.8 J (reference 11 and 12). The TPS61094 could support the supercap operation until supercap voltage is down to 0.7 V. So the supercap will discharge from 2 V to 0.7 V, the total discharge power is

Equation 3. GUID-20210201-CA0I-KRKR-2XZJ-QQSMXG1J53HT-low.gif

The supercap discharge power should be higher than the total loss of NB-IoT transmission, 4.8 J, so smart meter could choose 3 F supercap.