OTP based Analog Trimming and Calibration

Embedded NVM technology based functions can be implemented in large SoC designed in advanced technology nodes down to 28nm, as there is no requirement for extra mask levels, like when integrating Nand Flash, negatively impacting the final cost. And it is also possible to integrate One Time Programmable (OTP) to store trim and calibration settings in an analog device, usually designed in more mature technology node, so that the device powers up already calibrated for the system in which it is embedded. Variations in chip processing and packaging operations result in deviations of analog circuits and sensors from their target specifications. To optimize the performance of the systems in which these components are placed, it is necessary to “trim” interface circuitry to match a specific analog circuit or sensor. A trimming operation compensates for variations in the analog circuits and sensors due to manufacturing variances of these components.

Sidense 1T-Fuse™ technology is based on a one transistor non-volatile memory cell that does not rely on charge storage, rendering a secure cell that can not be reverse engineered. The 1T-Fuse™ is smaller than any alternative NVM IP manufactured in a standard-logic CMOS process. The OTP can be programmed in the field, during wafer or production testing.

In fact, the trimming requirement becomes more important as process nodes shrink due to the increased variability of analog circuit performance parameters at smaller processes, due to both random and systematic variations in key manufacturing steps. This manifests itself as increasing yield loss when chips with analog circuitry migrate to smaller process nodes since a larger percentage of analog blocks on a chip will not meet design specifications due to variability in process parameters and layout.

Examples where trimming is used include automotive and industrial sensors, display controllers, and power management circuits. If you look at the superb car at the top of the article, you realize that OTP technology can be implemented in several chips used to build “life critical” systems: Brake calibration, Tire pressure, Engine control or temperature or even Steering calibration… The field-programmability of Sidense’s OTP allows these trim and calibration settings to be done in-situ in the system, thus optimizing the system’s operation. Other examples where automotive trimming and calibration operations occur include secure vehicle ID (VID) storage, in-car communications, infotainment systems. The examples in the figure are for trimming and calibration of circuits such as analog amplifiers, ADCs/DACs and sensor conditioning. There are also many other uses for OTP, both in automotive and in other market segments, including microcontrollers, PMICs, and many others.

The above picture is a MEB view of the 1 Transistor OTP technologies, illustrating very interesting characteristics helping to guarantee high security level, pretty useful in SC industry today. In fact, the 1T-OTP bit-cell is very difficult to reverse engineer, as there is no difference between programmed and un-programmed bit. And, for applications requiring safe storage for secure keys, code and data, 1T-OTP macros incorporate other features for additional security, including a differential read more (no power signature), and probably a bunch of features that should be discussed face to face with Sidense!

A wide range of 1T-OTP macros are now available in many variants at process nodes from 180nm down to 28nm, and the technology has been successfully tested in 20nm. The company’s focus looking ahead is on maintaining a leadership position with NVM at advanced process nodes and solutions focused on customer requirements in the major market segments, including mobile and handheld devices, automotive, industrial control, consumer entertainment, and wired and wireless communications.

Eric Esteve from IPNEST