Low-Power Bluetooth SoC Fits Automotive Applications

What you’ll learn:

• How the DA14533 BLE chip reduces power.
• What connectivity and security features are integrated into the device?

One of the factors limiting range in an electric vehicle (EV) involves the weight of the car, which is typically 20% to 30% heavier than internal combustion types due mostly to the batteries. However, other elements contribute to the total weight of an EV, such as the wiring. Up to 70 different sensors require wires in an EV, which adds up to many kilograms. 

Bluetooth can replace those wires via wireless sensors, bringing kilograms of weight savings to the vehicle. And that, of course, helps improve range. 

One example is the tire pressure monitoring system (TPMS). Essentially, there are two types of TPMS: direct TPMS (dTPMS) and indirect TPMS (iTPMS). In dTPMS, the tire pressure is measured directly by a pressure sensor. In iTPMS, the tire pressure is obtained from the wheel speed via a wireless connection from the wheel to a central control unit.

The wireless technology used is a sub-GHz proprietary protocol. These solutions give drivers a warning when the tire pressure drops below a set threshold and can show the pressure for each wheel/tire on the dashboard display screen. The shift to Bluetooth will enable connection to smartphones. 

A shortcoming of all current TPMS solutions is that they can’t automatically identify individual wheels on the vehicle—you have to tell them. If, for any reason, two wheels are swapped, the central control unit will not know unless you manually reset the system.

BLE Chip Cuts Power Consumption

Recently, Renesas Electronics introduced a new Bluetooth chip that combines a radio transceiver, an Arm M0+ microcontroller, memory, peripherals, and security features in a compact system-on-chip (SoC) design. With its software stack qualified against Bluetooth Core 5.3 and ability to handle temperatures from −40 to +105°C, developers can support applications ranging from tire pressure monitoring and keyless entry to wireless sensors and battery-management systems. 

The DA14533, the first automotive-qualified device in the company’s Bluetooth Low Energy (BLE) SoC family, includes power-management features to simplify system integration and reduce power consumption. The device includes an integrated DC-DC buck converter, which adjusts the output voltage according to system requirements.

This SoC can function as a standalone application processor or as a data pump in hosted systems. Low power is achieved using the integrated low-I_Q buck-boost DC-DC converter, which remains active during sleep in buck mode. 

Active system power consumption is said to be lower than comparable devices in the market, requiring only 3.1 mA during transmission and 2.5 mA during reception. In hibernation mode, the current drops to 500 nA. 

These power-management and power-saving features help extend the operational life of small-capacity battery-powered systems. They also meet the stringent power requirements of tire pressure monitoring systems’ mission profiles.

Connectivity and Security Features

The DA14533 has dedicated hardware for the link layer implementation of BLE and interface controllers for enhanced connectivity capabilities. The BLE firmware includes the L2CAP service layer protocols, Security Manager (SM), Attribute Protocol (ATT), Generic Attribute Profile (GATT), and Generic Access Profile (GAP). All profiles published by the Bluetooth SIG as well as custom profiles are supported.

The AEC-Q100 Grade 2 qualified device also contains security features to safeguard connected devices from various threats thanks to its Bluetooth 5.3 qualification. 

Similar to other Bluetooth LE SoC devices in the Renesas SmartBond Tiny family, the DA14533 only requires six external components, offering a low engineering bill of materials (eBOM). 

A single external crystal oscillator (XTAL) is used for both active and sleep modes, eliminating the need for a separate oscillator in sleep mode. Its ultra-compact design—it’s housed in a WFFCQFN 22-pin, 3.5- × 3.5-mm package—makes the device the smallest automotive BLE SoC on the market, according to Renesas. With its compact design and low eBOM, the device integrates seamlessly into space-constrained systems, reducing overall system costs and accelerating time-to-market for customers. 

The DA14533 is available today, along with the BLE SoC Development Kit Pro (DA14592-016FDEVKT-P). The kit includes a motherboard, daughterboard, and cables to facilitate application software development. The daughterboard is also available separately to simplify development. This kit is specifically designed for software application development and power measurements.