Analog front ends (AFEs) can range in frequency from Hertz to GHz. With regard to complexity, at one end of the scale we have an op amp with a filter. At the other end we have a full signal conditioning front end, intermediate analog signal processing, an ADC, perhaps a microcontroller unit (MCU), and sometimes even more functionality (which sort of defeats the definition of “analog front end”). AFEs will be the topic of the upcoming Integration Nation chat session. We will post the time for this chat in the next few days.
AFEs are great for designers because the devices give us quicker time to market. In addition, the high integration into a monolithic IC keeps internal components closer. This minimizes parasitics and IR losses. It also simplifies power supply bypassing.
There are specialized AFEs like the multi-channel AFE for digital X-ray detector, power-line communications AFEs, weigh scale/body composition AFEs, camera/camcorder front ends, AFEs for process control, heart rate monitor front ends, radar AFEs, energy measurement front ends, metering front ends, and smoke detector front ends — just to name a few.
To give a quick overview, here is a brief listing of some AFEs and their manufacturers.
- ADI: AD73311, AD9920, AD7195, AD7730, ADAS1000, AD73360, AD73322
- Exar: XRD98L59, XRD98L23, XRD9818, XRD98L59, XRD9827, XRD98L24, XRD9826, XRD98L25, XRD98L63, XRD9816, XRD98L61, XRD9836, XRD9824, XRD9827
- Intersil: ISL51002, ISL98003, ISL98002, ISL51002
- Maxim (the sponsor of this site): 73M1903, MAXQ3181, MAX5865, MAX19706, MAX19707, MAX19710, DS8005, MAX5864, MAX19700, MAX5866, MAX19705, MAX19708, MAX19713, MAXQ3183, MAX19700, 78M661x
- Microchip: MCP3911, MCP3901, TC500, MCP3903, TC510
- ST: E-STLC7550
- TI: LMP90100, LMP91002, LMP90077, AFE030, LMP90078, ADS1191, LMP90079, LMP91000, LMP90080, LMP90097
I would like to highlight some very unique AFEs and comment on their analog integration content.
(Source: Texas Instruments)
First, there is the Texas Instruments LMP90100, a multi-channel, 24-bit sensor AFE that has continuous background calibration and sensor diagnostic routines. This AFE can interface with multiple types of sensors all at once. It can interface with RTDs, thermocouples, pressure sensors, load cells, and other voltage output sensors.
The way it does this is through an input mux, two matched current sources, sensor diagnostics, an embedded PGA with gains settable from 1 to 128V/V, and a 24-bit delta-sigma ADC. In my opinion, this is just the right amount of integration for a functional IC like this — any more and it might be overkill and any less would sacrifice needed functionality to quicken time to market for designers.
Another unique AFE series is the Maxim Integrated Teridian series embedded energy-measurement SoC (system on chip) family. The 78M661x family has a polyphase AC power measurement IC, single-phase AC power measurement IC, power distribution measurement IC, and an AC power monitoring IC. See Maxim Integrated’s website for more details and the 78M6610 review.
(Source: Maxim Integrated)
The Maxim SoC takes eight single-phase AC outlets and measures the outputs of voltage and current sensors into a mux and into a delta-sigma converter. There is also a reference, battery and temperature monitors, and programmable FIR filter. In my opinion, the AFE ends at the ADC, but Maxim has been able to successfully add an MCU, display driver, and memory onboard so the device is actually classified as an energy measurement SoC.
So where do you think the line should be drawn in AFEs solutions? How much is too much as it relates to analog integration or just integration in general? Please give us your thoughts at our upcoming chat. Keep watching for the date and time.