Nexperia — How to Simplify Voltage Translation

How to Simplify Voltage Translation in Today’s MCU- and MPU-Based Circuits

By Vikram Singh Parihar, Senior Product Manager (Interface Segment), Nexperia

Modular and scalable microprocessor and microcontroller systems operate at lower I/O and core voltages today than was common in the past. This presents a challenge to the designer, to efficiently connect data and control interfaces with older, legacy peripherals. The Autosense family of voltage translators from Nexperia helps to ease this problem by providing an integrated and flexible voltage-translating interface. The Nexperia voltage translators can be used for both high-speed push-pull buffered and open-drain applications.


The past decade has seen significant change in CMOS technology for microcontroller and microprocessor-based systems. Customer demand for smaller systems, longer battery life, and reduced Bill-of-Materials (BoM) cost has resulted in the rapid adoption of lower-voltage and lower-power I/O standards operating at levels down to 0.7V. This trend is noticeable not only in portable and wearable devices, but also in the industrial and automotive markets.


This means that today’s applications need to use a mix of I/O voltages and power supplies. For example, core digital control and data processing sub-systems often use a supply voltage of 1.2V or lower. Most of the analog and mixed-signal peripherals with which these digital devices interact, however, operate at 3.3V or even 5V. Interfacing multiple signals and devices operating in different voltage domains can create complex system requirements, requiring multiple voltage translators to bridge devices, signals, and I/Os.


Addressing Increased Complexity of Multi-Voltage Systems

Naturally any voltage difference can be bridged by using a single translator or level shifter, so that mixed-voltage systems can interoperate as required. But when a microcontroller, as the master, and multiple peripherals, as the slaves, operate at different voltage levels and need to send and receive data via an asynchronous bidirectional interface, the use of integrated translators will reduce the system complexity (see Figure 1).


With new signal standards constantly emerging, many of today’s systems transfer data at much higher rates than before, often at more than 100Mbits/s, and need to comply with tight requirements for propagation delay and channel-to-channel propagation skew. This is especially the case in consumer or telecoms interfaces such as Management Data Input Output (MDIO) and Secure Digital Input Output (SDIO).


So when the need arises for high speed, bidirectional, multi-voltage level translation, Nexperia’s Autosense portfolio can assist engineers in simplifying designs with a cost effective solution in a small form factor. The portfolio consists of the LSF010x, NXS010x and NXB010x series of voltage-level translators.

Figure 1: An Autosense voltage translator provides for communication between multiple I2C slaves operating at different voltage levels

All devices in the portfolio have wide voltage ranges, allowing a single device to shift levels for a broad range of new and legacy processors and peripherals. With the addition of automatic direction sensing to these bidirectional transceivers, no external Direction pin is required. This not only matches well with the latest low-voltage MPUs, allowing data to flow to and from any logic device, but it also offers another way to reduce BoM cost in space-constrained designs.


Optimized Interface Performance

The value of integrated level-shifting solutions becomes more evident as the number of data lines that need to be shifted increases. As well as providing substantial BoM cost savings, these integrated translators eliminate any timing or reliability concerns that might arise with the use of multiple single translators.


In addition, Nexperia has optimised the 1-, 2-, 4-, and 8-bit Autosense portfolio to meet the needs of different interfaces (see Figure 2). For example, the NXS and LSF devices can be used for both push-pull buffered and open-drain applications, making them ideal for simple IC-to-IC interfaces such as I2C, SMBus, PMBus®, 1-wireBus, and GPIOs.


Alternatively, NXB devices can be used in high-speed push-pull topologies. They offer very good signal integrity, making them better suited to port communications circuits, including HDMI, serial peripheral, UART and USB interfaces. Moreover, Nexperia’s patented NXS architecture helps to avoid reflections and improves driver capability over longer trace lengths up to 1m.

Figure 2: A comparison table of the Autosense portfolio of voltage translators


The PMBus name and logo are trademarks of SMIF, Inc.

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