Below Application note describe how to Add AA battery using Recom R-78S board to SensiBLE or SensiSUB and extend a battery life time for a very long time.
SensiBLE 1.0 and SensiSUB 1.0 originally coming with Coin Battery CR2032 with 220mAh that can power the board for demo only.
For a real applications often Application require to add external batteries to extend the battery life time.
R-78S Product Information
RECOM's R-78S switching regulator has been specifically designed for single-cell powered IoT applications. Due to its wide input voltage range, high efficiency and low stand-by losses, it extends the working lifetime of the cell. Based on the simple plug-and-play concept of the standard R-78 buck regulator, the R-78S boost regulator is able to provide a stable 3.3 VDC output from a lower input voltage from 3.15 V to as low as 0.65 V. Applications such as microcontrollers, WLAN / Bluetooth / LoRaWAN modules or IoT systems can now be supplied from a single 1.5 V cell.
The commonly used button cell provides approximately 3.2 V, but after a few hours of operation the voltage starts to decrease to 2.7 V – 2.85 V. This lower input voltage can cause problems in devices powered by typical solutions. In radio modules such as WiFi, Bluetooth and LoRaWAN, the range will be restricted and transmission will be disturbed. Using an R-78S and a AA battery offers considerably more power for a longer operational life. The efficiency of the R-78S series can reach 93% at full load and 90% under low load. It offers a low standby power consumption of only 7 μA when switched off with the integrated control pin. It can be operated in ambient temperature range from -40°C to +100°C and is certified to the new EN62368-1 standard.
A battery lifetime of 10 years doesn’t have to continue to be utopian.
One AA battery with 2100mAh can supply 7µA for 24 years.
In the application example shown here, the R-78S can be put into sleep mode, where it is then powered by its own output through an external buffer capacitor so that it only consumes 7 µA.
Therefore, the whole example application above only draws about 20 µW from the capacitor. After a certain discharge time, the voltage of the capacitor drops below a predefined threshold, waking up the application yet again. When the application is in sleep mode for too long, a watchdog function wakes up the R-78S, stopping the voltage of the capacitor from decreasing further and preventing the shutdown of the microprocessor. In certain applications the microprocessor could also be triggered by an external “alarm” signal, waking the application up from sleep mode.
R-78S3.3-0.1-EVM-1/SBL-1 with the SensiBLE v1.0 module
When the application is active it draws about 200 µA, which allows the capacitor to be ready again for sleep mode; thus saving valuable battery life. The size of the capacitor has to be scaled according to the desired minimum sleep mode time and depending on the application, the battery life can be prolonged drastically to reach the mythical ten years.