Microchip’s 25AA256 – When Internal Flash is Not Enough

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)

Microchip’s 25AA256 and 25LC256 SPI eeproms provide a convinient “offline” storage facility for microcontrollers with SPI interfaces – up to 256 kbits can be stowed away safely.

Seeing Microchip introduce SPI flash memory might look funny at first glance – the Americans are, after all, known for various microcontrollers with extremely ingenious remanent memory features. Most of them, however, have two limits: the amount of memory tends to be limited, writes tend to lock up the CPU due to resource congestion.

Should you ever find yourself in such a rut, do not fret – both 25AA256 and 25LC256 are ready to be of aid. Deploying them could not be easier from a technical point of view – our figure shows the pinout; an application schematic is not needed due to the simplicity.

…The pinout of the 25LC256 could not be easier

As with almost all other SPI peripherals, these SPI EEPROMs are quite flexible in terms of bus speeds. The datasheet claims that the bus can be run at up to 10MhZ, with erase and write operations usually taking around 5ms. Page size is said to be 64 bits, cells are expected to survive one million write operations.

In general, the bus implementation behaves just like any other SPI peripheral. However, the HOLD pin is interesting – it allows you to disable the memory controller, thereby repurposing the bus to control other hardware.

Given that these SPI flash memory ICs are intended to work with various microcontrollers, the components offer wide supply voltage ranges. The Microchip 25AA256 is able to work from 1.8V to 5.5V, while the Microchip 25LC256 has a lower limit of 2.5V. Nevertheless, both parts are ideally suited to work as Arduino flash memory – if you ever need to add additional storage space to your single board computer, this is the part to have on hand. The power consumption of about 5mA during operation is handleable for small microcontrollers – in standby, about one Microamp is consumed.