SLVAF41A March 2021 – November 2021 TPS61094

4 Solution Comparison

There is a summary of these three power solutions in Table 4-1. TPS61094 could provide a cost competitive and long lifetime solution in the smart meter. This solution can help smart meter customers exchange hybrid layer capacitor (HLC) to supercap, which could have lower total solution cost.

The TPS61094 with the supercap solution can support 18.4 years and increase operation time by 20% than the pure boost solution. And because the TPS61094 shares the same inductor and input/output capacitors in the supercap charging and discharging, the TPS61094 reduces component count by 50%.

Table 4-1 The Smart Meter Power Solution Comparison

Solution	Lifetime estimation (years)	Advantage	Disadvantage
The direct battery connection solution	18.1	Simple design	Big size HLC1550 (Tadiran)
The pure boost(TPS61094 or TPS610995) solution	14.9	Smaller size HLC and no sensitivity to the vendor, like SPC1520	Cannot get the maximum LiSOCl₂ capacity because LiSOCl₂ discharge current is uncontrollable LiSOCl₂ discharge end-off voltage is uncontrolled; it may have unrecoverable effects on the battery lifetime
The TPS61094 with the supercap solution	18.4	Cost competitive with the supercap Control LiSOCl₂ discharge current and end-off voltage Automatically transition; No need for MCU control	The supercap has leakage current, need to use lower terminal voltage, like 2 V

Solution

Lifetime estimation (years)

Advantage

Disadvantage

The direct battery connection solution

18.1

Simple design

Big size HLC1550 (Tadiran)

The pure boost(TPS61094 or TPS610995) solution

14.9

Smaller size HLC and no sensitivity to the vendor, like SPC1520

Cannot get the maximum LiSOCl₂ capacity because LiSOCl₂ discharge current is uncontrollable

LiSOCl₂ discharge end-off voltage is uncontrolled; it may have unrecoverable effects on the battery lifetime

The TPS61094 with the supercap solution

18.4

Cost competitive with the supercap

Control LiSOCl₂ discharge current and end-off voltage

Automatically transition; No need for MCU control

The supercap has leakage current, need to use lower terminal voltage, like 2 V

Note:

The smart meter lifetime estimation is based on the following conditions:

Calculation is based on Tadiran(LiSOCl2 TL-5920) and the capability de-rated according to the Figure 1-2.
Assumption that ten months is 25 ℃ and two months' temperature is lower than 0 ℃.
NB-IoT power consumption is about 134 mAh each year at supply voltage is 3.6 V
LiSCL2 Battery self-discharge: 25 ℃: 1 % / year, 40 ℃: 2 % / year
Hybrid layer capacitor self-discharge: 25 ℃: 3 μA, 40 ℃: 6 μA
Super capacitor leakage current: for 3 F cap, working at 2.0 V can reduce the leakage current to 20 %, the leakage current: 25 ℃: 1 μA (5 μA * 20 %), 40 ℃: 2 μA
Battery activation is about 30.4 mAh each year
Valve power consumption is about 35.8 mAh each year
Standby power consumption (including MCU, counting hall sensor, anti dismantling hall sensor, power supply, NB-IoT standby power consumption) is about 87.6 mAh.