Ricoh Co Ltd developed a basic technology to realize a reference voltage generator that can be driven by a power supply voltage of +1V or less.
In general, bandgap reference voltage generators, which utilize the temperature characteristics of bipolar transistor's base-emitter voltage (VBE), are used for low-voltage applications. However, in this method, the bandgap of silicon material is about 1.25V, and it is not possible to drive a reference voltage generator by a voltage lower than 1.25V. Furthermore, the use of bipolar transistor increases power consumption.
It is possible to realize a reference voltage generator for low-voltage applications by using a MOS (metal oxide semiconductor) transistor if its circuit architecture is improved. For example, a reference voltage generator can be realized by using transistors that have different threshold voltages (Vth). However, in this method, the variation in Vth causes the fluctuation in reference voltage. And, when Vth is lowered to decrease power supply voltage, leak current increases.
This time, Ricoh developed a technology to have a stable reference voltage of +1V or less without a high leak current by using MOS transistors. The company formed two MOS transistors whose gate materials are different and utilized the temperature characteristics of the difference between the gate materials' work functions.
Ricoh plans to commercialize the new technology in 2011. Because a reference voltage generator using the technology can be driven by a power supply voltage of +1V or less, it is possible to supply a reference voltage earlier than any other systems constituting an electronic device. Therefore, it might eliminate the need for complicated boot sequence control, the company said.
http://techon.nikkeibp.co.jp/e..._EN/20100809/184929/
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