Wide Arc of Technology and Applications
The term “analog” is loosely defined, and therefore people have different understandings of what “analog foundry” means. Analog designs, mixed-signal radio frequency (RF), and high-voltage (HV) and power technologies covering those areas fall under the umbrella of “analog” or “analog/mixed-signal,” and analog technologies can be categorized as follows:
- Analog Designs (big A /little D): A digital signal is defined at discrete values of time and amplitude (voltage). In contrast, an analog signal is defined across a continuous range of time and amplitudes. The real word is analog, not digital. Its signals, whether a current, voltage, pressure or inertial signal, need to be sensed and transferred to the digital domain for further digital signal processing. Analog designs have a large amount of pure analog circuits and a rather small amount of digital content. Typical applications are sensor front-ends, analog/digital converters (ADCs) and comparators.
- Mixed-Signal/RF Design: Mixed-signal/RF design typically is used for applications in the RF range. It requires the integration of digital circuits and fast, highly linear analog signal processing used for receiver and transceiver circuits at frequencies higher than 500Mhz. WLAN, Bluetooth and ZigBee radio applications are typical.
- HV Technologies: Digital circuits are limited to their core and I/O voltages that, depending on the process node, fall between 1.1V and 5V for the core and 3.3V and 5V for the I/O. In many cases, higher voltages than that are required for applications such as power management, power conversion and lighting. Voltages can go as high as 700V for power net applications and drive currents up 1A. Voltages between 5V and 40V are most frequently used.
- Power Technologies: Power technologies handle HV and high current at the same time, typically at process nodes of 0.60-micrometers and above. Fewer digital gates are integrated in circuits that handle power, whose currents exceed those on the HV side. Depending on the process architecture, currents up to 20A peak are possible. The boundaries between HV and power are somewhat fluid. Motor drivers, linear regulators and lighting are typical power applications.
Many analog applications require the combination of analog circuits, mixed-signal RF, HV and power, or a subset. Unlike the digital world where only a few capabilities suffice, addressing analog requirements calls for a wide range of different technologies.
Embedded non-volatile memory (NVM) capabilities are needed for trimming, data or program storage. Process and design IP architectures for embedded NVM are different for mixed-signal applications than digital applications. For digital applications, the embedded NVM blocks dominate the chip area that requires a very dense memory cell. Even if this comes with more than five additional layers, it is still cost-effective. For analog-dominated, mixed-signal designs, it is important to have a low mask count NVM solution available. The most complex functional integration would be “logic+analog+HV+NVM,” which would add too many process layers and would not be very cost-efficient. Therefore, a lean process architecture for the full-functional integration of logic, analog, HV and NVM is required.
Analog/mixed-signal devices often are required to work in a harsh, unfriendly environment, where they must cope with significant temperature differences, HV, switching noise or interference from neighboring elements.