Achieving a 10-Year Battery Life with Bluetooth Low Energy and Proprietary Wireless Protocols

For lots of little, portable Web of Things (IoT) applications, the “Holy Grail” is wireless connection with a battery life of up to 10-years, using a coin cell. This is not an easy task, as many affordable coin cells supply a maximum capability of only ~ 240 mAh. By picking a radio SoC with low rest existing intake, ten years is very possible for both long-distance as well as brief cordless connections.

In order to acquire 10-year battery life for reduced coin cell capacities like 240 mAh, cordless gadgets commonly spend the majority of their time asleep, just awakening periodically to make a cordless transmission, as illustrated in Figure 1 below. A 7 msec wake time, family member to a 5 2nd transfer period (120 wireless transmits per hour), yields a responsibility cycle of 0.14% wake time and 99.86% sleep time. This is why reduced deep rest power intake is crucial for accomplishing 10-year battery life from a coin cell.

Figure 1. Rest as well as Wake Time Responsibility Cycles

To accomplish a 10-year battery life, Bluetooth Low Energy is the preferred option for short to tool range cordless connection, usually 30 to 50 meters depending upon Transmitting (Tx) as well as Receiving (Rx) power. For longer distances, anything over 1000 meters, Sub Ghz Software application specified radios (SDR) are perfect.

Marketing

Bluetooth Low Energy runs in 2.4 GHz ISM band using a 40-channel dividers, spaced 2 MHz apart. The advertising channels (Figure 2) are alloted in different parts of the spectrum to supply resistance versus interference from 802.11/ Wi-Fi.

Figure 2. Bluetooth Low Energy Advertising And Marketing Networks (Resource Accton Advertising And Marketing).

Marketing Packets.

The information system of a promotion packet called the Protocol Data Unit (PDU), has a two-byte header that defines the type and also size of information payload as much as 37 bytes (6 bytes for the advertisement address and also approximately 31 bytes for information).

Figure 3. Bluetooth Low Energy Advertising And Marketing Packet (Source Accton Marketing).

Non-connectable vs. connectable.

Bluetooth Low Energy advertisement packages can be either Non-connectable or connectable. Figure 4 depicts the RSL10 System in Bundle (RSL10 SIP) Bluetooth Low Power module captured by a Power Analyzer for the Connectable (left) and also Non-connectable (best) “3 Promotion” events, both at 0 dbm Transmit Power. While both occasions make use of networks 37, 38 and 39, as well as last 7 msec, the Connectable event includes an RX pulse for each and every channel. This makes sense since the Connectable event likewise wishes to get. The resulting Power Analyzer dimension reveals the average present for each and every- 711.624 uA for Connectable, and also 504.307 uA for Non-connectable. The RSL10 SIP’s deep rest current is 160 nA for a 16 kbB RAM retention for the Bluetooth Low Energy stack, and running an inner timer to wake itself up.

Figure 4. Non-Connectable vs. connectable Advertising Packets.

RSL10 SIP Battery Life (5 Bytes).

Offered the conditions described over, Figure 5 demonstrates that the RSL10 SIP Actual Battery Life will certainly range from 10.97 Years (2.5 second Ad Interval, Connectable) to 27.26 years (5 2nd Advertisement Interval, Non-Connectable). These computations are based off making use of a 240 mA CR2032 coin cell as well as 5 byte information transfer (PDU).

Figure 5. RSL10 SIP Actual Battery Life.

Suitable Battery Life vs. Actual Battery Life.

Li-ion coin cells included information sheets that outline the Continuous Discharge Attributes for an offered lots. In the CR2032 battery instance in Figure 6, the story captures the discharge contour for a constant 19 0uA tons. The RSL10 SIP average current captured in Figure 5 ranges from 865 nA to 1.57 uA, much lighter than the 190 uA contour.

When I calculate the “Ideal VBAT”, I coulomb matter 240 mAh from 100% full to 0% empty, represented by the red dashed line labeled “Ideal VBAT”. A coin cell will certainly never ever in fact behave like the red dashed line. Recognizing that the “Real VBAT” discharge contour lies somewhere in between the red rushed line and also the blue CR2032 190uA discharge curve, I have actually de-rate the “Suitable VBAT” by 15% to reach the green “Actual VBAT” discharge curve.

Figure 6. Constant Discharge Features.

If we raise the information size from 5 Bytes to 31 Bytes, Figure 7 listed below exposes the RSL10 SIP battery life.

Figure 7. RSL10 SIP Battery Life (31 Bytes).

Proprietary RF Protocols.

Proprietary Sub-GHz radios are designed for longer distance cordless transmissions. With a web link spending plan of 153 db (16 dbm Tx power with a -135 Rx level of sensitivity), the AXM0F24 narrow-band SoC can transmit a range of 37km, or 23 miles (915MHz, 30db fade margin). For a 1.1 kilometres range, the AXM0F243 goes beyond the desired 10-year Actual Battery Life.

Figure 8. AXM0F243 Actual Battery Life.

With the best radio SoC, accomplishing a 10-year battery life for brief and also long-ranges is entirely possible. Find out more regarding ON Semiconductor’s options for connection today.