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data transmission in the car: bluetooth low-energy for short-range radio
the ubiquity of bluetooth low-energy means that literally everything is connected to the smartphone today. Of course, this also applies to our cars – or at least to some interesting automotive features.
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Bluetooth low-energy and smartphone connectivity are ubiquitous in the automotive sector.
The phone has already become part of the vehicle system, which means that a standard radio solution must be present in the car. While the type of radio technology used is changing, the technical requirements for applications such as tire pressure monitoring systems (TPMS), key fobs or phone-as-a-key remain:
- Reliable communication
- Low latency
- Very low operating power consumption
- Continuous operation without draining the battery too much
Bluetooth low-energy meets these requirements, and its strengths in the automotive sector can be demonstrated by the example of the key fob (key fob with unlocking/locking function). These are small, portable and require a very long battery life – usually over many years. They appear to be doing "nothing" most of the time, but are actually in sleep mode, ready to communicate when needed and when within range of the vehicle. Therefore, low power radio operation is essential. When a button is pressed to unlock a car door, it must be done immediately, without any noticeable delay, so that the user feels in control of the car. Therefore, low latency and reliable communication are also a prerequisite. The ubiquity of bluetooth also offers the interesting possibility of using a cell phone instead of the conventional key fob.
Reliable communication
The modern key fob is not only used for locking/unlocking a vehicle. It can also be used to locate a vehicle in a large parking lot or to remotely start the vehicle to warm it up on a cold winter day. The driver is not always in close proximity to the vehicle, so communication between the key fob and the vehicle must be reliable over a longer range – even if the transmission/visibility path is partially blocked by people, vehicles or other obstacles. Bluetooth low-energy has an unobstructed line-of-sight range of tens of meters, providing more than adequate range in a normal parking lot.
Another aspect of reliability is responsiveness. Because users today expect near-instantaneous response, bluetooth low-energy communication must operate with very low latency. The time difference between pressing the unlock button and unlocking the vehicle doors must be unnoticeable to the driver. bluetooth low-energy operates with very low latency, which is due to the fact that in such a system the networked systems/assemblies are virtually always on. When not in use, they can enter a power-saving/sleep mode from which they can wake up and operate much faster than when turned off. However, the advantage of being on all the time should not be at the expense of power consumption.
Low power consumption
Bluetooth low-energy is (as the name suggests) a radio communication technology with very low power consumption. Given the success of battery-powered consumer devices, which have a limited power supply, the use of this technology in the automotive sector is inevitable. A key fob may average 20 key presses per day, each lasting approximately 6.2 ms, resulting in a total daily operating time of only 124 ms. For the rest of the day, the key is in a passive energy saving mode. During this time, power consumption must be minimized so as not to drain the battery.
when the key fob is in use, its active power consumption must be as low as possible to prolong the life of its (usually) 3V button cell battery. Although a car battery is larger and more powerful, a key fob is used to lock/unlock the vehicle when the car is off. Since the engine is not running, this operation uses idle power at a time when the battery cannot be recharged. in addition to the other systems such as the clock, the engine computer’s internal memory and the radio presets that also consume battery power when the car is not running, the key fob transceiver in the vehicle must also be economical when it comes to power requirements.
Bluetooth low-energy wireless socs are now readily available from numerous vendors worldwide. The number of vendors and resulting price competition make bluetooth low-energy a more cost-effective off-the-shelf solution today than proprietary devices with short-range radio-based communications. In addition, the small size and light weight of the components ensure that no bulk or weight is added to the system. Both are important considerations in the automotive industry, where every gram and cubic millimeter saved relates to reduced empty weight and fuel efficiency.
Another important factor that has contributed to the introduction of bluetooth low-energy in the automotive sector is safety. From pairing and key generation to data exchange, bluetooth low-energy has been designed from the ground up to be a secure radio-based communication tool. After all, no one wants key fobs or other people’s smartphones to be able to unlock their own car! All these benefits make bluetooth low-energy an advantageous option for radio-based communication over short distances in automotive applications.
ON semiconductor’s NCV-RSL10 is a bluetooth 5-certified radio soc qualified for automotive applications. It offers the industry’s lowest power consumption in receive and deep-sleep modes and consumes only 25 na power in deep sleep (I/O wake-up) when powered from a 3 V supply. With its low power consumption, the NCV-RSL10 ensures negligible discharge of the main battery in the vehicle, longer battery life (in the vehicle or key fob) and smaller product size due to a smaller battery (in the key fob) and energy harvesting in tire pressure monitoring systems (TPMS).
Other important aspects for components used in automotive applications are safety features and the ability to meet demanding safety standards and high reliability requirements. The NCV-RSL10’s 7 mm x 7 mm QFN housing with wettable flanks allows manufacturers and oems to perform automatic visual inspection (AVI) after assembly -a common requirement and part of the production process today. The soc device also has an integrated AES128 encryption accelerator to protect sensitive data and is AEC-Q100 grade 2 qualified, which covers the temperature range from -40 to + 105 °C.