Low-power eFlash block optimised for IoT devices

The 128-kbit eFlash, which is available as an 8 k x 16-bit IP block is based on Silicon-Oxide-Nitride-Oxide-Silicon (SONOS) Flash technology. X-FAB has built up extensive experience in integrating SONOS memories with conventional CMOS processes, ensuring high levels of data reliability. The IP block has been designed for low power mixed-signal applications and features a deep power down stand-by mode consuming a maximum of 50nA.

The new X-FAB eFlash IP block is targeted at replacing standalone NVM memories and embedded One-Time-Programmable (OTP) memories in low power applications, enabling onsite programme code updates. This means that it is suited to energy harvesting and remotely located IoT devices, where power constraints and harsh environments need to be dealt with, but field re-programmability must be offered at a low cost.

X-FAB has rigorously qualified the eFlash IP block to comply with the AEC-Q100 standard, so that it offers engineers an automotive-grade solution capable of operating across a temperature range of -40 to 125°C. The SONOS technology enables reliable operation of the IP block when combined with high-voltage (HV) options ranging from 6-45V. This is made possible by the NMOS, PMOS and DMOS transistors available with X-FAB’s 180nm XH018 process. High field reliability is enabled with a number of test modes explicitly designed to test individual memory bit cell currents and achieve 0PPM in the field. Finally, special test modes have been designed into the IP to optimise production testing and minimise test time and cost.

With this latest release, X-FAB's complements its existing NVM portfolio with this very low power option. Other available Flash blocks address automotive applications up to 175°C in read operation.

Combining the fast read/write speeds of a conventional SRAM with the non-volatility of an EEPROM, the NVRAM compiler facilitates generating and integrating memories from 1 to 16-kbits in a range of applications requiring fail-safe memories. The contents of the SRAM can be backed up to the EEPROM memory resource in the event of a power failure. This proves to be a highly desirable feature for safety-critical applications - such as smart meters, industrial control devices or data transfer systems.

The NVRAMs can be re-programmed up to 100,000 times at 35°C and up to 10,000 times at 175°C. NVRAM blocks generated by the compiler can retain data for up to 20 years without battery power in high temperature environments (125°C). Innovations in the test logic integrated with the NVRAM reduce the test time by avoiding time-consuming measurements for low currents, thereby reducing production test costs.

Thomas Ramsch, Director NVM Development at X-FAB, sums up the benefits as follows: “The combination of different NVM options with high-voltage features and low-leakage properties at a low mask count make the XH018 process a highly effective, reliable and cost-efficient solution for emerging energy harvesting and IoT devices. With the introduction of these readily available silicon-qualified NVM IP, we are enabling designers to focus on bringing their products to market faster and cheaper.”