A 1.5V, 8mW, 8 b, 15Msps BiCMOS A/D Converter

Recently digital signal processing has become very popular in video signal processing systems. Analog-toDigital (A/D) converters in this field, namely, video A/D converters, are also popular and have been integrated into mixed-signal system LSIs. Both power consumption and power supply voltage of video A/D converters have been decreasing drastically in recent years [1], [2]. One of the applications of video A/D converters is for hand-held multimedia terminals, which require long-term battery operation and small batteries. Video A/D converters embedded in mixed-signal system LSIs for this use are thus required to operate at a low supply voltage with small power consumption in order to reduce the system power dissipation and to reduce the number of battery cells. Since digital LSIs for multimedia terminals can operate at 1.5V supply voltage [3], A/D converters integrated into these digital LSIs would be also required to operate at 1.5V. Video A/D converters also need to have more than 8 b resolution; While high definition TV requires 10 b resolution, 8 b resolution is allowable for portable use. In this paper we report a 1.5V BiCMOS 8b 15Msps video A/D converter developed by combining the high transconductance and good matching of bipolar transistors with the circuit flexibility of a MOS switched capacitor circuit technique. This BiCMOS A/D converter shows analog BiCMOS has potentially higher performance than CMOS even at 1.5V power supply voltage. In Sect. 2, problems in low voltage analog circuits are discussed initially, then A/D converter design concepts to overcome the problems are described. The