AD2S93

a FEATURES Full Function Monolithic LVDT-to-Digital Converter Absolute Serial Data Output Uncommitted Differential Input Repeatability Remote Diagnostics 14-Bit Resolution Industrial Temperature Range 28-Pin PLCC Low Power APPLICATIONS Industrial Gauging Industrial Process Control Linear Positioning Systems Linear Actuator Control Automotive Motion Sensing and Control Torque Sensing Conditioner AC Strain Gages Conditioning Avionics REFERENCE (PRIMARY EXCITATION) Low Cost LVDT-to-Digital Converter AD2S93 FUNCTIONAL BLOCK DIAGRAM C3 ACERROR ERROR AMP AC RATIO BRIDGE R6 C4 R5 DEMODIN REF DIFFERENTIAL (SECONDARY A VOLTAGE) B R4 GAIN DIFF R3 VDD LOS OVR UNR NULL CS LATCHES LOS DECODE LOGIC UP-DOWN COUNTER PHASE SENSITIVE DEMODULATOR DEMOD OUT R1 R7 INTIN C1 R2 C2 VEL VCO GAIN DIR CLKOUT FREQUENCY SHAPING VCO DATA SCLK SERIAL INTERFACE AD2S93 GENERAL DESCRIPTION The AD2S93 is a complete 14-bit resolution tracking LVDT-todigital converter. A Type II tracking loop is employed to track the A–B input and produce a digital output equal to (A–B)/ (REF/2), where REF is a fixed amplitude ac reference phase coherent with the A–B input. This allows the measurement of any 2-, 3-, 4- and 5-wire LVDT or linear amplitude modulated input. The operating frequency range is from 360 Hz to 10 kHz with user definable bandwidth set externally within a range of 45 Hz to 1250 Hz. The AD2S93 has a 16-bit serial output. The MSB (LOS), read first, indicates a loss of the signal A, B, or reference ...