Monthly Archives: November 2013

Translating between voltages in mobile applications

In mobile systems, where power consumption and size are always a concern, it can be hard to manage system peripherals with different voltage requirements. Our level translators, housed in tiny, mobile-friendly packages, make the job easier.

If you’re designing a mobile system — a phone, a tablet, or an eReader, for example — then you’re probably dealing with a lot of different voltages, especially along the serial interface. The application processor may output a low voltage to the I2C or SPI bus (maybe 0.8, 1.8, or 2.5 V), but the peripherals that the serial bus connects to — the display subsystem, the GPS receiver, the HDMI output — probably use a different voltage, ranging from 1.8 to 3.3 or even 5 V. Satisfying the voltage requirements of these various peripherals can be a real challenge, especially if you’re trying to maintain power efficiency and a very small footprint.

That’s where we come in. Our level shifters for mobile give you a compact, efficient way to connect the application processor to just about any peripheral.

Figure 1 gives an overview of the system voltages in a generic mobile platform and highlights the NXP products that can help streamline the voltage issues.

fig1

Figure 1. Level shifters for mobile platforms

As shown in the diagram, our portfolio includes single- and multi-bit level shifters to support a variety of peripherals. We offer devices that perform bidirectional translation without a direction pin, and support bus frequencies from 100 kHz to 20 MHz. An Enable pin (EN) controls the connection and disconnection on both sides of the device, and the device schematics are simple to understand and easy to work with.

For example, a one-bit device like the NVT2001 is a good choice for use with clocks and interrupt lines, while a four-bit device for SPI is better suited for use with the camera module. We have an 8-bit level shifter for use with RGB displays, and offer a dedicated level shifter for SIM cards, for use in single- and dual-SIM applications. In general, though, a bidirectional, two-bit level shifter for the I2C bus, like the NVT2002, may be the most versatile, giving you the most options for connectivity.

NVT2002 level shifter

The NVT2002 is a dual, bidirectional voltage-level translator that works with the I2C bus or the SMBus. It performs bidirectional level translation without a direction pin, and can translate any voltage between 1.0 and 5.5 V. It provides lock-up free operation for isolation when the EN pin is set low, and it delivers excellent ESD performance of HBM 4 kV. The PCA9306 is the same as the NVT2002, but with a lower ESD rating of HBM 2 kV. Both devices are available in tiny, mobile friendly packages, including the XQFN8 (1.6 x 1.6 x 0.5 mm) and the XSON8U (1.35 x 1.0 x 0.5 mm). Figure 2 shows the NVT2002/PCA9306 in an application that uses voltages ranging from 1.2 to 3.3 V.

fig2

Figure 2. Sample application of NVT2002/PCA9306 level translator

Other options

The NVT2002/PCA9306 provides simple translation without capacitance isolation. If capacitance isolation is important for your design, we recommend some alternatives, shown in Table 1. The PCA9x17 translates between a standard I2C master and a low-voltage slave, and the PCA9509x translates between a low-voltage master and a standard-voltage I2C slave.

Table 1. Select I2C level shifters

 

PCA9517A

PCA9617A

PCA9509A/P

PCA9306

NVT2002

Rise-time accelerator

No

No

No

No

No

Idle/stop detect for hot-swap

No

No

No

No

No

Noise/offset isolation

Yes

Yes

Yes

No

No

Capacitance isolation

Yes

Yes

Yes

No

No

VCCA or VCC supply range

0.9 to 5.5 V

0.8 to 5.5 V

0.8 to 1.5 V

N/A

N/A

VCCB or VCC2 supply range

2.7 to 5.5 V

2.3 to 5.5 V

2.3 to 5.5 V

N/A

N/A

ESD HBM

5 kV

5 kV

2 kV

2 kV

4 kV

 

The PCA9517A is a drop-in replacement for the PCA9517, which has a lower ESD rating of HBM 2 kV. The PCA9617A is a Fast Mode plus (Fm+) version of the PCA9517A. It supports the wider voltage range associated with 1-MHz Fm+ devices. The PCA9x17A has no offset on the A side and static offset on the B side, and can be configured in parallel or series (Figure 3).

fig3

Figure 3. Parallel and serial configurations

In the parallel (star) configuration, the PCA9x17 is connected from A to A, and in the series configuration, from A to B. The series configuration is possible because the voltage between the A and B ports can be aligned.

The PCA9509P is the same as the PCA9509A, except without the current source on the low-voltage A port. The PCA9509P uses an external pull-up on the A port, since it has no internal current source, but this makes it possible to customize the settings and, as a result, configure the circuit to have much lower current consumption (less than 0.95 mA for the PCA9509P compared to less than 1.9 mA for the PCA9509A). Either version of the PCA9509 can be connected in parallel, from B to B, but, because the voltage between A and B ports of the PCA9509x can’t be aligned, neither version supports a series configuration.

Just the Beginning

Our level shifters are a good place to start if you’re looking to manage voltages in your mobile design. For the rest of your system, our interface portfolio offers standard I2C device building blocks like, GPIO expanders, camera LED flash drivers, LED dimmers and blinkers, RTCs, temp sensors, proximity sensors, and high-speed interfaces. We’re also a leading supplier of logic products and discrete solutions.

Bottom line — no matter what kind of mobile system you’re designing, we have components that will help you improve performance and get to market quickly at mobile.interfacechips.com. For more ideas about mobile applications, explore the other areas of our website (www.nxp.com) or contact your local NXP representative.

Let us hear from you

Are you designing a mobile system? If so, we’d like to hear about it. Leave a comment to share an experience, pass along a design trick, or ask a question.

Making building automation more efficient, more interactive

Buildings are getting smarter, making it easier for property managers and consumers to save energy and control their surroundings. NXP has a broad range of solutions for building automation, but two items in particular — RTCs and capacitive sensors — help designers make their systems more precise and easier for people to use.

In recent years, having ready access to several technologies, including low-power microcontrollers, wireless connectivity, and low-cost sensors, has made it easier for designers to develop advanced systems that making buildings smarter and help save energy. What once may have sounded like science fiction has become fairly routine: thermostats that automatically respond to changes in their surrounding environment, ceiling lights that turn themselves on and off depending on the occupancy of the room, being able to use a cell phone to control a building’s HVAC, security, and fire-safety systems.

By and large, systems for building automation are built around a central microcontroller that manages tasks and interacts with the connectivity interface. Figure 1 gives a generic system-level block diagram, highlighting the components NXP supplies.

Building Automation Diagram 131001

Figure 1. High-level block diagram for a typical building-automation system

As shown in the diagram, NXP can support just about every portion of the design, but there are two interface products in particular — the real-time clock (RTC) and the capacitive sensor — that can be especially important to the designer because they help boost two things — efficiency and ease of use — that are attractive to end users. In this article, we take a closer look at NXP’s RTC and capacitor-sensor offerings.

Precise, low-power RTCs

It’s been said that timing is everything. In building automation, timing functions, which can help a system turn on or off at a given time or track the duration of a particular activity, can be a significant factor in saving energy. Precision, durability, and power consumption are some of the key things to look for in an RTC.

The NXP portfolio for RTCs includes several families, each optimized for a particular characteristic, like power, cost, accuracy, or temperature. In addition to time-keeping functions that clock from seconds to 99 years, RTCs in the portfolio offer low power consumption (PCF2123 with Icc of < 100 nA), cover a large voltage range (1.5 to 5.5 V), include programmable timers, generate a frequency output, operate off the I2C or SPI bus, and are housed in small packages (TSSOP8, HVSON10) that save space and lower overall cost. Table 1 gives an overview.

Table 1. Highlights of the NXP RTC portfolio

Key feature Highlighted products Comment
Ultra-low power consumption PCF8523, PCF2123 < 100 nA, I2C or SPI interface
Low power with low cost PCF85063 Tiny package, I2C or SPI interface
High accuracy PCF2127, PCF2129 ±3 ppm, I2C and SPI interface
Extended temperature range PCA8565, PCA21125 Up to 125 °C, I2C or SPI interface
AEC-Q100 compliance PCA2129/Q900 Highly accurate, automotive

For applications that require timing references with the highest accuracy, the PCF2127 and PCF2129 are available in versions that offer typical error rates of just ±3 ppm. The PCA2129 is recommended for use in systems that will be exposed to harsh conditions, since it’s available in an AEC-Q100 compliant version that withstands the challenging environment of a car engine. The PCF2123, with its ultra-low power consumption, also offers electronic tuning, for added design flexibility. The PCF8523, another RTC designed to reduce power consumption, offers electronic tuning along with other features that help manage the use of power, including power fail detection, battery switch-over, and battery-low detection. The PCF85063 is the smallest RTC we offer and can be ordered in an HXSON8 (2.1 x 3.1 x 0.5 mm, 0.5-mm pitch) or HXSON10 (2.7 x 2.7 x 0.5 mm, 0.5-mm pitch) package. Many of these devices are available in evaluation kits that help designers experiment with functionality.

Capacitive sensors for better user interfaces

Capacitive sensors, which are also called proximity sensors, use human body capacitance as an input and can be used to detect position or displacement, humidity, fluid level, or acceleration. In terms of user interfaces, capacitive sensors enable touch-sensitive interactions, like those used with trackpads on laptop computers or touchscreens on mobile phones or tablet computers.

NXP offers a series of highly sensitive, highly configurable, and low-power capacitive sensors that can improve the user interface in several ways. No contact is required (the touch area doesn’t actually have to come in contact with a finger), so a person can operate the system even if they’re wearing gloves. The ability of the capacitive sensor to perform self-calibration means the interface can be used in dirty environments, and when proximity protection is embedded in the equipment the interface becomes tamper-proof, too. A capacitive sensor can also be used in combination with any event that generates a pre-defined change in capacitance, so the system can be made more responsive. Lighting systems, fans, blinds, medical and industrial equipment, machinery in public restrooms — all these things can benefit from using a capacitive sensor.

The NXP PCF8883 is a single-channel capacitive sensor that can operate on its own, without a microcontroller. The PCA8886, which is AEC-Q100 compliant, is a dual-channel sensor that can be used for up to three sensors without a microcontroller. The PCF8885 is an eight-channel sensor that requires a microcontroller. It can be configured for up to 28 sensors and, with two devices, can enable up to 80 sensors. The PCA8885 is an automotive version of the PCF8885. All NXP’s capacitive sensors are available in evaluation kits, reference designs, or application boards that make it easier for engineers to get started with a design.

Just the Beginning

RTCs and capacitive sensors can be essential components if you’re working on a design for building automation. For the rest of your system, our interface portfolio offers standard building blocks like LCD drivers, bus buffers and voltage translators, general-purpose I/O expanders, temp sensors, and more. We even have UARTs, bridges, muxes and switches, and LED controllers, along with other specialty products that support building automation, like Power-Line modem solutions and stepper motor controllers that support HVAC compressors and blowers as well as variable-speed fans and pumps.

Bottom line — no matter what kind of system you’re designing for building automation, we have components that will help you improve performance and get to market quickly. For more ideas about building automation, explore the other areas of our website (www.nxp.com) or contact your local NXP representative.

Let us hear from you

Are you designing a system for building automation? If so, we’d like to hear about it. Leave a comment to share an experience, pass along a design trick, or ask a question.

Interface components for a smarter metering system

Today’s utility meters, equipped with microcontrollers and wireless connectivity, track usage more precisely and help consumers use resources like water, gas, and electricity, more efficiently. NXP’s interface portfolio offers a wide range of innovative options for designing best-in-class eMeters.

Utility companies around the world are seeing the value in upgrading to new, microcontroller-based meters equipped with wireless connectivity. These devices are able to track the use of gas, electricity, and water more precisely, and can transmit usage data to a central location. Utility companies can monitor usage in real time, to analyze trends and respond more quickly to increases in demand. Having eMeters in place makes it easier to implement tiered pricing systems, since usage can be time-stamped and billed accordingly, and eliminates the need for personnel who drive from meter to meter, taking readings. This saves on overhead and also reduces greenhouse emissions.

The eMetering trend is good for consumers, too, since it gives people more information about how they use resources. Having a website that lets consumers view their usage can be a good way for people to gauge the efficiency of household tasks, and can give guidelines on how to save resources and money.

Most eMeters follow a similar setup, whether they’re used to track water, gas, or electricity. The main component is a microcontroller, which monitors usage and works with a wireless interface to transmit data. What typically makes one eMeter different from another is what the device is used to monitor. An eMeter that monitors water or gas usage, for example, typically has a valve driver for controlling the flow of water or gas, while an eMeter that monitors electricity doesn’t usually need a valve. Figure 1 gives a high-level block diagram for a water or gas eMeter. The block diagram for an electricity eMeter would be similar, but without the valve driver.

eMeter article diagram 131011

Figure 1. High-level block diagram for a typical eMetering system for water

As shown in the diagram, NXP can support just about every portion of the design, from the microcontroller and RF components to the power supply and logic functions. NXP’s interface portfolio includes options that make it easier to implement the sensor and actuator functions, as well as the various system interfaces.

Advanced temp sensors

Temperature sensors are an important part of the metering function, since they calibrate the front-end data. They’re also needed for on-board measurements that support system management. Today’s temp sensors provide very precise temperature measurements, but they also can be used to set windows for interrupts, alarms, and other system-level functions. NXP offers a large selection of temp sensors, including local sensors, combination local/remote sensors, and thermal sensors. These devices are available in a wide range of packages, and there are a number of options for very small footprints. The LM75B, for instance, is a digital temp sensor and thermal watchdog available in 8-pin packages that measure just 2 x 3 mm.

Table 1. Highlights of the NXP temp sensor portfolio

Part number Accuracy SMBus timeout
LM75A ±2 °C No
LM75B ±2 °C Yes
SE95 ±1 °C No
SE98A ±1 °C Yes
SE97B (with 2k EEPROM) ±1 °C Yes

For applications that need local and remote sensing, we recommend either the NE1617A or the SA56004. Both offer accuracy to within ±2 °C for local sensing. For remote sensing, the NE1617A delivers accuracy of ±3 °C, while the more precise SA56004 delivers an accuracy of ±1 °C.

Highly accurate RTCs                     

The NXP portfolio for real-time clocks (RTCs) includes several families, each optimized for a particular characteristic, like power, cost, accuracy, or temperature. In addition to time-keeping functions that clock from seconds to 99 years, RTCs in the portfolio offer low power consumption (PCF2123 with Icc of < 100 nA), cover a large voltage range (1.5 to 5.5 V), include programmable timers, generate a frequency output, operate off the I2C or SPI bus, and are housed in small packages (TSSOP8, HVSON10) that save space and lower overall cost. Table 1 gives an overview.

Table 1. Highlights of the NXP RTC portfolio

Key feature Highlighted products Comment
Ultra-low power consumption PCF8523, PCF2123 < 100 nA, I2C or SPI interface
Low power with low cost PCF85063 Tiny package, I2C or SPI interface
High accuracy PCF2127, PCF2129 ±3 ppm, I2C and SPI interface
Extended temperature range PCA8565, PCA21125 Up to 125 °C, I2C or SPI interface
AEC-Q100 compliance PCA2129/Q900 Highly accurate, automotive

Efficient, easy-to-use LCD drivers

The LCD display is a central component of most meters, because utility workers and consumers want to be able to see the meter reading, even if the meter also transmits data wirelessly to a remote location. NXP has been a leader in LCD technology for more than 25 years, building on the reliable chip-on-glass (COG) technology used in the automotive industry. All our new LCD drivers are designed for 15 kV ESD performance, and comply with the automotive standard AEC-Q100. Our LCD drivers are ideally suited for driving Vertical Alignment (VA) displays, which deliver high contrast, a true-black background, and a wide viewing angle.

Our portfolio includes segment drivers, character drivers, and graphic drivers. The segment drivers are standalone devices that require very little power,  drive up to 640 segments, and can be cascaded together. The character drivers combine a low-power segment display with a sophisticated 2-line character display and can be used in display shirt or static display modes. The graphic drivers include on-chip generation of LCD bias voltages, offer low power consumption, and require very few external components.

Segment drivers are likely to be the best choice for eMetering applications. Here are some recommended options:

Table 2. NXP segment drivers for eMetering

Product Segments
PCF85162 4 x 32
PCF85176 4 x 40
PCF85134 4 x 60
PCF85133 4 x 80
PCF8536 8 x 40

Just the Beginning

Temp sensors, RTCs, and LCD segment drivers are essential components in eMeters of all kinds, but they’re just one part of the design. For the rest of your system, our interface portfolio offers standard building blocks like bridges, voltage translators, GPIO, and more. We also have capacitive sensors, which use human body capacitance as an input, for use in touch-sensitive interfaces like trackpads and touchscreens.

Bottom line — no matter what kind of eMeter you’re designing, we have components that will help you improve performance and get to market quickly. For more ideas about building automation, explore the other areas of our website (www.nxp.com) or contact your local NXP representative.

Let us hear from you

Are you designing an eMeter? If so, we’d like to hear about it. Leave a comment to share an experience, pass along a design trick, or ask a question.