Using NXP’s NXQ1TXH5 Qi Charging Circuit

MicroCrystal RV-8803 – A Really Accurate RTC June 17, 2019- RTC chips traditionally were the domain of Maxim and NXP. Switzerland-based MicroCrystal recently made quite a buzz with its RV-8803, which offers simple integration, an I2C interface and extreme accuracy. Let us start out by looking at a system overview. Figure one shows how this I2C RTC is made up internally – interested observers note … Continue reading MicroCrystal RV-8803 – A Really Accurate RTC
Analog Devices’ LTM2887 – If a Digital Bus Needs Galvanic Isolation June 15, 2019- In theory, digital buses are intended to connect things to one another. Sadly, one sometimes wants but a logical connection – in many cases, galvanic isolation helps out. Should you ever feel like isolating very fast buses, definitely give the LTM2887 a chance. From a technical point of view, Linear Technologies attempt at entering the … Continue reading Analog Devices’ LTM2887 – If a Digital Bus Needs Galvanic Isolation
AVAGO APDS-9008 or APDS-9005-020 – Keeping an Eye on Ambient Light June 14, 2019- Recent times saw quite a bit of interest for part numbers such as the APDS-9008 or APDS-9005-020 – they are a very interesting type of ambient light sensor. One of the oldest questions in regards to light sensors involves their spectral sensitivity. If a part is to output but one voltage level, the conversion between … Continue reading AVAGO APDS-9008 or APDS-9005-020 – Keeping an Eye on Ambient Light
STMicroelectronics’ LIS2DH12 – Low Power Motion Sensing June 12, 2019- Apple’s iPhone introduced gyroscopic sensors to a wider range – before that, accelerometers were not commonly found in consumer hardware. STM sells excellent parts which, however, get little media attention – time to take a look at the LIS2DH12. Integrating the part into your circuit as an MPU6500 alternative or MPU9500 alternative is not difficult. … Continue reading STMicroelectronics’ LIS2DH12 – Low Power Motion Sensing
Panasonic AMG8833 – FLIR for cheap June 7, 2019- FLIR made infrared thermal sensors cool – sadly, their parts are all but cheap (and suffer from export control problems). Panasonic’s Grid-EYE family is a low-resolution alternative which comes at significantly lower cost. From a technical point of view, Panasonic’s image sensor could not be simpler. We are looking at an 8×8 sensor with an … Continue reading Panasonic AMG8833 – FLIR for cheap
DipTronics DTS-62R-V – Small Switch, Very Big (and Very Cheap) June 5, 2019- When yours truly was but a lowly cadet, various US manufacturers produced (pricey but quite reliable) switches. Chinese vendors recently started to catch up – seeing the DTS-62R-V top our customer interest list shows that the run stage of the crawl-walk-run cycle is reached. DipTronics has been around the Asian switch market for ages, exhibiting … Continue reading DipTronics DTS-62R-V – Small Switch, Very Big (and Very Cheap)

QIck charging

Adding wireless charging to furniture and other consumer goods is a nice way to add some oomph to an otherwise boring product. NXP’s NXQ1TXH5 provides an interesting, albeit difficult-to-prototype way around the problem.

Creating a Qi-compatible is as easy as assembling the example circuit shown in figure one. From a technical point of view, the diagram is full of decoupling capacitors but does not require much in terms of complexity. The main issues are a) finding a correct coil and b) prototyping the device – NXP uses a 5 mm x 5 mm, 32-pin HVQFN package which is not really suited to non-reflow soldering processes.

some people would call this circuit a capacitor’s grave

…some people would call this circuit a capacitor’s grave

Advanced functionality

While most charging ICs limit themselves to simply providing the oscillating field needed for transferring power, NXP adds a few extremely nifty features to its chip. First of all, the NXQ1TXH5 is able to monitor and restrict the amount of power supplied to its clients. This way, multiple chips can power themselves from a single USB wallwart. Sadly, this process does not have unlimited efficiency – look at figure two to see a power derating curve.

QI’s already-bad efficiency becomes terrible if but small amounts of power are to be transferred

…QI’s already-bad efficiency becomes terrible if but small amounts of power are to be transferred



User convenience is enhanced by the presence of LED and buzzer outputs: emitting a satisfying beep as charging starts makes handling the charger so much more pleasant. Finally, the part also has an I2C interface, which is not documented.

Power consumption is reduced via a dedicated pinging circuit. When no device is present, NXPs chip hibernates the main Qi charging system and emits special waveforms to detect hardware – this way, standby can be accomplished with minimal power consumption.

Sadly, the public datasheet of the part is short and tardy – developers who want to use the chip in anger should ask their local NXP office for further information and/or a more detailed set of documents.