AD7750

a FEATURES Two Differential Analog Input Channels Product of Two Channels Voltage-to-Frequency Conversion on a Single Channel Real Power Measurement Capability < 0.2% Error Over the Range 400% Ibasic to 2% Ibasic Two or Four Quadrant Operation (Positive and Negative Power) Gain Select of 1 or 16 on the Current Channel (Channel 1) Choice of On-Chip or External Reference Choice of Output Pulse Frequencies Available (Pins F1 and F2) High Frequency Pulse Output for Calibration Purposes (FOUT ) HPF on Current Channel for Offset Removal Single 5 V Supply and Low Power G1 V1+ V1– x16 Product-to-Frequency Converter AD7750 FUNCTIONAL BLOCK DIAGRAM VDD ACDC ADC1 2ND ORDER MODULATOR HPF ADC2 V2+ V2– x2 REVP DELAY CLKOUT CLKIN MULT 2ND ORDER MODULATOR DTF 2.5V BAND GAP REFERENCE LPF F1 F2 AD7750 REFIN FS S1 S2 DTF FOUT AGND REFOUT DGND GENERAL DESCRIPTION PRODUCT HIGHLIGHTS The AD7750 is a Product-to-Frequency Converter (PFC) that can be configured for power measurement or voltage-tofrequency 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 highpass 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 outp...