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Where Is Analog Integration Going?

Since the birth of monolithic integrated circuit (IC) technology, analog circuit designers have looked for a quick path to new precision, compact and low cost system designs. This approach would integrate many of the standard IC functions into a new highly integrated semi-custom monolithic chip. The cost of a full custom chip was too expensive in those early days.

The 1960s
The first baby steps in the early 1960s was “discretionary wiring” on bipolar “master dice breadboards”[1] using gold ball wire bonds. These were intended as prototype devices.

Figure 1

Master Dice Bread Board

Master Dice Bread Board

Figure 2

Schematic of the available devices on the chip

Schematic of the available devices on the chip

Figure 1 shows a chip without the wire bond interconnect and Figure 2 shows the schematic of the “breadboard chip” components. Figure 3 shows a “breadboard chip” with a rat's nest of wire bonds. If breadboarding was successful, the chip would be metalized for production.

Figure 3

The chip configured as a prototype IF amplifier

The chip configured as a prototype IF amplifier

As the analog chips became more complicated, this approach was later replaced with the “master slice” process using one or two metal layers to interconnect the transistors, resistors, and capacitors as a semi-custom design (see Figure 4). Interdesign/Ferranti/Zetex (now Diodes Inc.) popularized the “Mono-Chip.” Many other semiconductor companies had similar semi-custom bipolar analog arrays.

The 1970s
Hybrid circuits using discrete transistors, thick and thin film resistors, and ceramic capacitors on a ceramic substrate with interconnecting gold patterns were a precursor to monolithics. Later on hybrids started to integrate monolithic chips (see Figure 5) and many standard products such as analog to digital converters were developed and widely used. Analog CMOS started to become mainstream as RCA Solid State and Intersil began offering all CMOS op-amps and other analog devices.

Figure 5

Thick Film Hybrid[2] Click here to see a larger image.

Thick Film Hybrid[2]
Click here to see a larger image.

Next, the 1980s – 1990s.

The 1980s – 1990s
When FPGAs first came out in the mid-1980s, we all wished that someone could invent something similar for analog design. The difficulties and complexities of analog design are not for the faint of heart. Thermal effects, parasitic components, critical electrical routing, cross talk, substrate currents, voltage breakdowns, and leakage currents are just a few of the critical issues the design engineer must deal with. FPAAs started to appear as shown in the time line in Figure 6.

Figure 6

Timeline marking important milestones in the field of FPAAs & FPMSAs (Field Programmable Mixed Signal Arrays) [3] Click here to see a larger image.

Timeline marking important milestones in the field of FPAAs & FPMSAs (Field Programmable Mixed Signal Arrays) [3]
Click here to see a larger image.

The 21St Century

Later on, multi-chip modules (MCMs[4] ) were developed to increase levels of analog integration and performance. An Agilent proprietary oscilloscope front end MCM is shown in Figure 7.

Circa 2013 Today, the newest packaging trend is System in Package (SiP) versus System on Chip (SoC); see Figure 8.

Figure 8

SoC vs. SIP design tradeoffs (Source:Toshiba)

SoC vs. SIP design tradeoffs
(Source:Toshiba)

What is System in Package? “System-in-Package (SiP) is more than an IC package containing multiple die. SiP products are fully functional systems or sub-systems in an IC package format. SiP may contain one or more IC chips (wire bonded or flip chip) plus other components that are traditionally found on the system mother board.”[5] . Thus, analog and digital components, passives, MEMs or RF components are combined to provide a sub-system or system function in a single IC package.

What is System on Chip (SoC)? “A system on a chip or system on chip… is an integrated circuit (IC) that integrates all components of a computer or other electronic system into a single chip. It may contain digital, analog, mixed-signal, and often RF functions — all on a single chip substrate.”[6]

A new approach from Triad Semiconductor that is focused on developing configurable analog and digital technology for the mixed signal ASIC market may be a step in the right direction. It's not a true FPAA but very close. See Related posts , below, for more details on this emerging technology.

Summary
Analog circuit designers are still waiting for FPAAs as the “Holy Grail” to have a quick path to new semi-custom monolithic designs. FPAAs have been around since the mid-1980s and have never broken into mainstream numbers on anyone's product forecast. As pointed out right here in Planet Analog by Scott Elder (Field Programmable Analog & Gallium Arsenide), “FPAAs are a non-starter.” Meanwhile, digital FPGAs are projected to be over a $3.5 billion market this year.

There are only two known mainstream FPAA suppliers remaining, Anadigm and Cypress with their PSoC. If you know of any others, please post their names in the comments section, below.

This week Cypress introduced a new development kit (CY8CKIT-033A) which looks very useful and very promising. See Figure 9.

Figure 9

CY8CKIT-033A PSoC 3 MFi Digital Audio Development Kit

CY8CKIT-033A PSoC 3 MFi Digital Audio Development Kit

Also available from Servenger using the Anadigm programmable chip is the “Programmable Analog Module (PAM) which is a multi-featured, tested and dependable solution that makes the functionality of the FPAA immediately usable, right out of the box. It can be used as a free-standing module or as a system component. The Servenger PAM is completely compatible with the AnadigmDesigner2 CAD design toolset”. (See Figure 10 below)

Figure 10

Servenger PAM using the Anadigm FPAA

Servenger PAM using the Anadigm FPAA

As mentioned in Brian Bailey's article Why Don’t Field Programmable Analog Arrays Work?, “I, too, would love to hear about companies that are using programmable analog systems. I'd like to make them feel welcome here. Do you know of any successful programmable analog projects [using FPAAs]?”

Whatever the case, we have evolved our analog design process from discretely connecting transistors to a systems approach. This is just a natural step as we take advantage of Moore's Law for analog integration.

References:

  1. Datasheet IC105A NM-3011, NM-3015 Norden-Division of United Aircraft. May 1965
  2. ICI (now Crane/Interpoint) Catalog circa 1984
  3. Design Approaches to Field-Programmable Analog Integrated Circuits DEAN R. D’MELLO AND P. GLENN GULAK, Department of Electrical and Computer Engineering, University of Toronto, Toronto, Ontario Canada June 11, 1997, Figure 17
  4. Personal conversation with Walter Becker, WB SALES
  5. Amkor data sheet for SIP
  6. Wikpedia definition of SoC

Related posts:

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