AD7750

The AD7750 is a Product-to-Frequency Converter (PFC) that can be configured for power measurement or voltage-to-frequency conversion. The part contains the equivalent of two channels of A/D conversion, a multiplier, a digital-to-frequency converter, a reference and other conditioning circuitry. Channel 1 has a differential gain amplifier with selectable gains of 1 or 16.Channel 2 has a differential gain amplifier with a gain of 2. A high-pass filter can be switched into the signal path of Channel 1 to remove any offsets.

The outputs F1 and F2 are fixed width (275 ms) logic low going pulse streams for output frequencies less than 1.8 Hz. A range of output frequencies is available and the frequency of F1 and F2 is proportional to the product of V1 and V2. These outputs of AD7750 are suitable for directly driving an electromechanical pulse counter or full stepping two phase stepper motors. The outputs can be configured to represent the result of four-quadrant multi- plication (i.e., Sign and Magnitude) or to represent the result of a two quadrant multiplication (i.e., Magnitude Only). In this configuration the outputs are always positive regardless of the input polarities. In addition, there is a reverse polarity indicator output that becomes active when negative power is detected in the Magnitude Only Mode, see Reverse Polarity Indicator.

The error as a percent (%) of reading is less than 0.3% over a dynamic range of 1000:1.The AD7750 is fabricated on 0.6 CMOS technology; a pro-cess that combines low power and low cost.