How to Select the Best Bluetooth LE Chipset for Your Needs

Before you choose a BLE chipset for your new great product what factors should you consider?
It is a good idea to evaluate available options before starting any project.
These are the topics we cover in this article:

• Bluetooth: Chip or Module?
• QFN or WLCSP?
• Bluetooth Vendors,
• Cost of BLE chipset,
• Technical Details and Features,
• Trends in Bluetooth industry.

At the Beginning

The first thing you need to be sure of is whether or not you need Bluetooth Low Energy or the Classical Bluetooth.
In other words, ask yourself what is more important: either bandwidth data transfer or time of autonomous work. If there is a need to work with audio streaming, or even sometimes the need to transmit in Megabytes per second then Bluetooth Low Energy doesn’t do what you need. But if autonomy of work is a crucial feature of the project and it’s OK to send/receive 1-3 Kb/s then maybe Bluetooth Smart is the best choice.

So then, how go about to selecting the most appropriate BLE chipset? There are two basic answers to this question.

Way #1, Simple. Just choose a well-tested chip by one of the most popular vendors. It could be one of Nordic’s chips for example. BLE chips produced by NS cover 60-70% of the market. These processors are time-proven by millions of active devices, well documented and have a free tools for developers.
If you need a classic solution this is a good way to go.
On the other hand, recently some companies have released solutions with interesting features like hi-tech and speedy core processors, supporting a wide range of different wireless specifications in one module. If your project is high-end it is better to probe deeper and try to explore:

Way #2, Advanced. Make sure you fully understand the main features of your final product and select the most appropriate solution.

Chip or Module?

A Bluetooth module is a small PCB that includes a Bluetooth processor along with other hardware needed to run the device. A typical BLE module often includes:

• Antenna (or antenna connector),
• Balun (antenna matching circuit),
• PA – Power Amplifier,
• LNA – Low Noise Amplifier,
• Crystals, or crystal oscillators that are needed to run the radio,
• Power components – these can include decoupling capacitors, inductors/chokes, and in some cases DC/DC converters,
• Non-volatile memory.

The Bluetooth chip is the core of a Bluetooth module. There is a CMOS processor that includes an Micro-Controller Unit MCU core, a 2.4 GHz radio that is 802.15.1 compliant, and has the ability to run a Bluetooth software stack either on-board, or with the help of a partner MCU.

Pros and cons

Both chip and module solutions have main benefits and disadvantages. Modules are typically more expensive, more challenging to manufacture than the processor itself, and contain many additional components. Modules are simpler to design into systems, and have the additional advantage that they have already passed certification testing which could save up to USD 10-50K in the design process.

Bluetooth processors are cheaper than modules, and allow you more flexibility in system design. Bluetooth processors are also smaller (it is easy to find size models 2.5 x 2.5 mm). The trade-off in this case is that, the product design process is significantly more complex for a processor versus a module. This option requires expertise in wireless system design, as well as software expertise to interface with the top level API of the Bluetooth stack. Bluetooth processors are also required to pass regulatory testing, and this is a major financial burden for processor based designs.

Bluetooth Processor benefits and disadvantages:

Bluetooth Modules benefits and disadvantages:

QFN or WLCSP?

If the size of a chip is important you can choose a chip that comes in a standard Quad Flat No Leads QFN package that is easy to use in products. You can also select a WLCSP-CSP or CSP – Wafer Level Chip Scale Package which is basically just the silicon die with solder balls, very similar to a Ball Grid Array (BGA).

The differences between QFN and WLCSP/CSP:

• QFN packages cost more and are larger, but are easier to use and can have less manufacturing issues.
• WLCSP/CSP packages are less expensive because they contain less material and undergo less processing. They are usually smaller, but require design experience and tighter tolerances along with more PCB layers. The printed circuit board (PCB) design for WLCSP devices require much tighter tolerances and usually more than 2 layers, so it is more expensive.

It’s critical to get the design and manufacturing right because a bad design or manufacturing issues could cause problems such as cracks in the balls. This is one of the main causes of low yields. WLCSP is good for very small products or modules where QFN won’t fit, but requires more effort in getting it right.[*]

Bluetooth Vendors

To be honest, there are no good or bad vendors are represented on the market of Bluetooth Smart processors. Each of them have different solutions with features that could be helpful for your product. These tier-one companies provide good live support and documentation. The main difference is in whether they provide proprietary or free development tools. In other words, you get what you pay for.

Bluetooth Hardware Cost

There are few ways to make a single device cost lower.

1. Purchase a lot of devices. The more devices that are bought the less each individual device will cost.
2. Work directly with the manufacturer. If you’re ordering 100K devices per year, you should be able to get single unit prices in the $0.90 – $1.25 range for a Bluetooth SoC.
3. Switching from tier 1 companies to the grey market. For many reasons this is a risky road to follow. But if the cost is the crucial question and the device configuration is possible to find from a less famous producer in China this may be the way to go. Of course in this case there may be no warranty or technical support.

Technical details

Your project will have a completely unique set of components and configurations that is suited for it. It is beyond the scope of this article to recommend a definite set of characteristics as good or bad for your project. But if you focus on the next four questions you will save time and money in the long run:

1. What set of hardware should the chipset contain? The best way is to hire a qualified developer who could tune the best configuration if you do not have one in-house.
2. How is accessibility and support of the BLE stack? Is it free or proprietary and does the vendor provide good documentation.
3. Is support of the microchip crucial for the project? Are you ready to pay for good support?
4. Which special features should the chip/module have? Let’s have a look at these a little in the following section:

BLE Features

1. Declared low energy consumption as a crucial feature.
2. Cutting-edge processors (like ARM Cortex-M4)
3. IoT Capabilities:
   • Low-power IP (IPv6/6LoWPAN)
   • Bluetooth Smart Internet Gateways (GATT)
4. Security
   • LE Privacy 1.2
   • LE Secure Connections
5. Speed
   Comparing to 4.1 BLE protocol, BLE 4.2 devices are:
   • 250% Faster
   • 10x More Capacity
   • Adapting to work in Mesh topology.

Bluetooth Trends

In the end it is not a bad idea to also pay attention to the current industry trends in BLE chipsets:

• Manufacturers moving to Bluetooth v4.2;
• More advanced CPUs: Cortex-M4 and M3 replacing M0, 8051 and 16-bit;
• Larger RAM and Flash to run more advanced applications;
• RF fully integrated in the device;
• Advanced peripherals requiring less CPU intervention;
• Multiple protocols in the same device.

We hope these this information helps you to make the right decisions.

Images sources: infinarium.com, gigaom.com.