Nordic Semiconductor’s RF System-on-Chip Supports Standard and Proprietary ProtocolsFebruary 22, 2020 by Robert Keim
This article briefly reviews some important principles of power-supply design before discussing the features of the nRF5340.
Providing clean, reliable, managed power is a crucial step in successfully designing embedded systems with high-performance ICs such as the nRF5340.
nRF5340. Image used courtesy of Nordic Semiconductor
First, you’ll need decoupling capacitors and maybe a ferrite bead or two, and you can read about this aspect of power-supply design in AAC’s Clean Power for Every IC series. You may also need to consider thermal issues, noise reduction (in both linear regulators and switching regulators), and circuitry for recharging a battery.
Supervising Your Power
In this article, I don’t want to focus on generating, modifying, or delivering power to ICs. Something else that we may need to do is “keep an eye on” our power rails by means of supervisory or monitoring circuits. This topic occurred to me as I was browsing the (781-page) datasheet for the nRF5340, which includes (among numerous other features) a power-supply supervision module:
Power-supply supervision module. Image used courtesy of Nordic Semiconductor
The basic purpose of a supervisor circuit is to detect imperfections in a power supply voltage. These imperfections are communicated in a way that helps the system to respond (if necessary), either by addressing the power-supply issue or by modifying the operational state of the load circuitry.
Supervision is especially important when we’re working with microprocessors because they’re “smart” enough to cause serious trouble if they don’t receive the electrical nourishment for which they’re designed.
Whereas simpler components such as transistors or amplifiers will generally fail in a relatively predictable and benign fashion, a processor powered by insufficient supply voltage might malfunction in a way that is more akin to “going haywire” or “running amok.” The peripheral operation might change, RAM data may be lost, instructions might execute incorrectly … and what if the processor was controlling a missile, or a medical device, or an industrial machine?
Numerous power-management ICs (such as the nanoPower from Maxim Integrated) are available to help you with your supervisory needs. Microcontrollers and other types of processor ICs frequently (nowadays, maybe almost always) include power supervision in the form of a power-on reset and maybe a brownout detector.
However, there’s no guarantee that this integrated module will meet the specifications of your particular application, and consequently, you may choose to supplement the processor’s capabilities with functionality provided by an external supervisor IC.
A (Very) Highly-Integrated RF Solution
The nRF5340 has a full-featured supervisor module with power-on reset, brownout reset, and a power-fail comparator that notifies the processor when the power supply voltage crosses thresholds configured by the user.
This, however, is only one item in a very long list of features:
- Support for Bluetooth 5.1, Zigbee, Thread, proprietary 2.4 GHz wireless communication, and near-field communication
- Arm CryptoCell-312 and 128-bit AES for secure operation
- Programmable RF transmit power up to +3 dBm
- RF receive sensitivity of –97.5 dBm at 1 Mbps
- USB, UART, SPI, and I2S for digital communication
- 12-bit, 200 ksps A/D conversion
Block diagram of nRF5340. Image used courtesy of Nordic Semiconductor
Are Two Processors Better Than One?
As you can see, this system-on-chip includes two independent Arm processors, each with its own bevy of peripherals.
One of these processors is called the “application core”; it supports digital-signal-processing instructions, has a single-precision floating-point unit, and operates at frequencies up to 128 MHz. The other processor, the “network core,” is optimized for low-power operation. It’s restricted to 64 MHz, has fewer features, and contains the wireless protocol stack.
Nordic states that the nRF5340 is the world’s first wireless-communication SoC that integrates two Arm Cortex-M33 processors. That makes me all the more interested in why exactly the chip has two processors. After reading the general description of the part and looking through the product brief, I’m still not clear on exactly how these two separate processors are intended to work together.
My best interpretation of the information that I read is that the application core is intended more for intense signal processing work, whereas the network core provides lower-power operation and implements the radio protocols. But this alone doesn’t really justify, at least not in my mind, the presence of two completely separate processors. I’d be interested to learn about why Nordic Semiconductor chose this dual-processor architecture and the specific advantages that it offers the designer.
Nordic indicates that design work involving devices in the nRF51, nRF52, or nRF91 series can be ported fairly easily to an nRF5340 project. If you have experience with any of these devices, feel free to share your thoughts in the comments section.