VFCs Feature On-Board Buffers

Dec. 1, 1999

With on-chip buffers for high input impedance and full-scale output frequencies up to 2.76 MHz, AD7741 and AD7742 voltage-to-frequency converters (VFCs) use the buffers to eliminate gain errors without degrading the accuracy of the resulting measurement. The devices use a synchronous charge-balancing architecture and guarantee 12-bit integral non-linearity over the automotive temperature range of -40°C to 105°C and industrial range of -40°C to 85°C. Input clock frequency ranges from 200 kHz up to 6.144 MHz for applications such as electric motor control, military radios, battery voltage monitoring, Internet access for cable modems, automotive GPS systems and more. The AD7742 provides two differential or three pseudo-differential input channels for improved signal conditioning, and its full-scale output frequency is specified up to 2.76 MHz over a VDD range of 4.75V to 5.25V and its common-mode voltage range is specified from 500 mV above GND to 1.75V below VDD. The AD7741 provides one single-ended channel and a common-mode voltage that extends down to 0V. Both converters include an on-chip 2.5V voltage reference.


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