An autonomous environmental monitoring sensor node is powered by a small rechargeable battery and managed by a low-power microcontroller containing a massive number of integrated silicon MOSFETs.
State the name of the chemical compound used to form the insulating layer beneath the gate terminal in an enhancement-mode N-channel MOSFET that prevents gate current from flowing, resulting in an extremely high input resistance.
The microcontroller’s CPU contains 2.5×1082.5 \times 10^{8}2.5×108 integrated MOSFETs. A discrete power MOSFET of a similar voltage class has a typical standby drain-to-source leakage current, IDSSI_{DSS}IDSS, of 4.0 nA4.0\text{ nA}4.0 nA.
The sensor node is powered by a lithium-ion battery with a capacity of 850 mA h850\text{ mA h}850 mA h. A fully charged reference battery of capacity 1 A h1\text{ A h}1 A h allows 3600 C3600\text{ C}3600 C of charge to flow. The manufacturer specifications state that the sensor node can remain in standby mode on a single full charge for ≈120 hours\approx 120\text{ hours}≈120 hours.
Discuss, using a calculation of the potential standby time if all integrated transistors leaked 4.0 nA4.0\text{ nA}4.0 nA, why the leakage current of the individual integrated MOSFETs on the CPU chip must be vastly smaller than that of the discrete MOSFET.
