Wires & Power Are the Limiters

Wires. We don't think of them a lot of the time, except perhaps when we are dealing with high-speed communications, but wires are an essential part of every system created. They get power to a device; they are used to connect sensors to processors and processors to displays. In a typical car today, wires represent the third heaviest and costliest component after the engine and frame. The average weight of wires in a car is now 150 kilograms, according to the IEEE Institute.

Much of this wiring has come about because of the slow but steady increase in electronics in the car. As each system was added, new wiring was added to the harness. Also, the need to have centralized fuses for wire harness protection makes wires longer than they need to be. In planes the situation is even worse. A 747 transport aircraft has 140 miles of wire in it, weighing 3,500 pounds. A plane fitted for passengers would take even more.

So, why am I talking about this? There are many systems where the wiring is a constraint, and wires are the big limiter for the progression of the Internet of Things (IoT). The IoT is dependent on having very small, cheap sensors that can basically be placed everywhere and can communicate to whoever needs their data. Given that these networks are ad-hoc and transitory, they cannot be wired networks.

There are many standards looking into ultra-low-power wireless communications, some that consume as little as 200μJ per hour. But what about the power connections? When these sensors get distributed into every light switch, into your clothes, into signs along the road — nobody wants to deal with changing the batteries or wiring up to a power source. They have to scavenge the power they need from their environment.

Solar, vibration, heat, and RF are the primary ways power can be derived from the environment, but the amounts they can reliably generate have to be matched to the power draw of the electronics. Not only that, but the power they provide is erratic, where both the voltage and amount of power available can vary over time. Small batteries or super capacitors can be used to hold charge, but this is already adding to the size, weight, and cost of the solution.

All of this places a large burden on the analog parts of a system, but at the same time, the analog components are vital to the success of such a system. A large amount of pioneering work has been done in the medical field where long battery life has always been a priority in the design; but more is required, and often this requires better models in order to design better circuits. Most analog design has been using BSIM3 and BSIM4 models that are based on threshold voltages.

A new BSIM6 model is a charge-based core derived from Poisson's solution and includes physical effects such as mobility degradation, velocity saturation, high frequency models, etc. The key advantage is that currents and derivatives are symmetric at Vds =0 and capacitances and derivatives are also symmetric around Vds =0. In addition the solution is continuous in all regions of operation. These models are necessary for FinFET modeling, which provides increased gain and reduced leakage compared to planar transistors. BSIM6 was released in May 2013 and is already incorporated into many commercial EDA tools.

How are the demands of ultra-low-power going to affect you? Will more accurate modeling help?

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16 comments on “Wires & Power Are the Limiters

  1. goafrit2
    August 2, 2013

    >> Will more accurate modeling help?


    Yes of course. The challenge in the small feature size is compounded by the need of low power.  The key problem is traced to the lack of good models for nanometer CMOS processes. Good models will be needed and that will help in the design of low power systems.

  2. BillWM
    August 3, 2013

    Am evaluating a TMS570 Micro-controller — it has a full Ethernet MAC with MDIO output — this can eliminate scores of wires, and connector pins(subject to effects of corrosion / thermal cycling), allowing more reliable connector pins/cable to be used.  It also features many channels of 12bit ADC and PWM for DAC and a special timer unit for things like engine timing control.   All the peripherals feature BIST, as does the Memory and CPU's(Dual Lock-Step ARM R4's at up to 180 MHZ).  It also has FlexRay, CAN, and LIN buses to reduce wire count, and low core power requirements and low core voltage for low EMI.  See my article in EETIMES under MCU design line.

    Also features ECC/EDAC on all memory, and Parity on all buses and peripherals for hard/soft error detection/handling.

  3. BrianBailey
    August 3, 2013

    The problem with Ethernet is that nobody with sign off on it for mission cvritical applications because of timing issues with colissions etc. I understand that in aircraft applications they developed a variant that they hoped would be approved but still they cannot get it signed off. I would image automotive would be the same. It is tough to guarantee timing and performance when you have a protocol that was not designed for real-time applications.

  4. BillWM
    August 3, 2013

    Brian – If you have flown on an A380, a 787, 747-800 a 737-800,900, or Now the NG you have at one point or another flown under ethernet control doing hard-real-time control of the aircraft.  



    I helped verify AFDX for the 787, and 747-800 at Rockwell Collins as a consultant.


    There also is MODBUS over Ethernet, and several other ethernet industrial control protocols by Rockwell, Emerson, Honeywell, and many many other companies doing hard real-time control of all manor of industrial and utility functions.


    Have even helped use ethernet to control brushless DC motors and do real-time vibration control in industrial, automotive, and Avionics applications — with the ethernet inside the motor it's self.



    Never said it used TCP/IP on a public network — It uses special eithernet cable, special connectors, standard or custom PHY, standard or custom MAC, and a custom stack.  (Also uses custom switches and routers)

  5. WKetel
    August 7, 2013

    Just a few years back there was a push and a hollar that autos were going to a four wire system, two power wires and two data wires and the whole thing would use ethernet or some variation for control. Also we were going to have a 42 volt system. 

    The very good news is that it didn't happen, It soon became clear that all of those smart little modules would cost a lot more, and that the pproblems with going to the 42 volts system were insurmountable. What I mean is that the actual cost of these wonderful systems was A LOT MORE than anticipated, and in addition it became clear that the resulting logistics nightmares would destroy the car industry. But somebody keeps digging up the corps and claiming that only a bit of makeup is needed. I think that they are wrong. The problems are two basic and fundamental.

  6. Brad_Albing
    August 11, 2013

    @Will Murray – what would say is the reliability of this as a communications link in an aircraft?

  7. Brad_Albing
    August 11, 2013

    @WKetel – yes, what ever did happen to the 42V automotive systems? It would have reduced some wire gauge sizes in some portions of the wiring harnesses. Tho' maybe not enough to matter much in terms of weight and cost. Similarly, relays and contactors might have gotten a little smaller, so maybe a small cost savings there. Of course, any solid state relays and power supply devices would be manufactured on a higher voltage process, so the cost goes up.

    No free lunch here….

  8. BillWM
    August 12, 2013

    @Brad — The spec for AFDX is one bad packet per 70million packets(CRC error) — The system relies on up to 5 different paths for the wire in the aircraft, so is fairly robust vs EMI at the system level — Typically it is tested to 400V/m for resistance to HIRF and will pass that(Spatial Diviersity Concept) — It typically is not used for extended temperature applications, but can be due to the more recent availability of 125 deg C phy's and magnetics.   One ethernet can replace 20 to 100 RS-485(CSDB) Bus cables.   It is complex and there are still ways to shoot one's self in the foot with it — but it can, and does work.


    For automotive, the drivers for eithernet introduction will be functions like vision, and other high resolution sensors for driver assistance, collision avoidance, and other items.

  9. Brad_Albing
    August 12, 2013

    @Will Muray – OK – that increases my personal confidence level. Thanks. I'll keep flying.

  10. WKetel
    August 12, 2013

    Presently, any problems with the electrical and mechanical portions of flying are far exceeded by the unpleasentness inflicted upon the travelers by the TSA. That organization has made flying so miserable that now I take the train. Really, trains are so much nicer that I may never go back to commercial airlines, until the TSA goes away.

  11. Brad_Albing
    August 12, 2013

    @WKetel – I agrre in principal, but for where I live and where I need to get to (e.g., CLE to PHX, SFO, or LGA), I pretty much must fly.

  12. WKetel
    August 12, 2013

    B_Ab, it does indeed appear that you have a problem. Unfortunately the railroad passenger routs have been terribly reduced over the years, and the Amtrak CEO does not even like trains. 

    But I think thatI would carefully examine how badly I really bneeded to go to those cities. As an example, after some bad experiences at the Canadian border I wrote that country off my lists for about 20 years. I choose to avoid places where the doorkeepers are hostile. 

  13. TheMeasurementBlues
    August 13, 2013

    And fly you shall.



    And if that doesn't work:



  14. Brad_Albing
    August 13, 2013

    @TMB – Thanks. And if those don't work out, I'll ride my bike.

  15. TheMeasurementBlues
    August 13, 2013

    Which bike?



  16. Brad_Albing
    August 13, 2013

    @TMB – This would be the non-motorized version. But it does have 2 wheels.

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