Datasheet AD71056 (Analog Devices) - 7

link to page 16 link to page 15 link to page 15
AD71056 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS VDD 1 16 F1 V2P 2 15 F2 V2N 3 14 CF AD71056 V1N 4 13 DGND TOP VIEW V1P 5 (Not to Scale) 12 REVP AGND 6 11 RCLKIN REFIN/OUT 7 10 S0
03 0 6-
SCF 8 9 S1
63 05 Figure 3. Pin Configuration
Table 4. Pin Function Descriptions Pin No. Mnemonic Description
1 VDD Power Supply. This pin provides the supply voltage for the circuitry in the AD71056. Maintain the supply voltage at 5 V ± 5% for specified operation. Decouple this pin with a 10 μF capacitor in parallel with a ceramic 100 nF capacitor. 2, 3 V2P, V2N Analog Inputs for Channel V2 (Voltage Channel). These inputs provide a fully differential input pair. The maximum differential input voltage is ±165 mV for specified operation. Both inputs have internal ESD protection circuitry; an overvoltage of ±6 V can be sustained on these inputs without risk of permanent damage. 4, 5 V1N, V1P Analog Inputs for Channel V1 (Current Channel). These inputs are fully differential voltage inputs with a maximum signal level of ±30 mV with respect to the V1N pin for specified operation. Both inputs have internal ESD protection circuitry and, in addition, an overvoltage of ±6 V can be sustained on these inputs without risk of permanent damage. 6 AGND Analog Ground. This pin provides the ground reference for the analog circuitry in the AD71056, that is, the ADCs and reference. Tie this pin to the analog ground plane of the PCB. The analog ground plane is the ground reference for all analog circuitry, such as antialiasing filters, current and voltage sensors, and so forth. For accurate noise suppression, connect the analog ground plane to the digital ground plane at only one point. A star ground configuration helps to keep noisy digital currents away from the analog circuits. 7 REFIN/OUT Reference Voltage. The on-chip reference has a nominal value of 2.45 V and a typical temperature coefficient of 20 ppm/°C. An external reference source can also be connected at this pin. In either case, decouple this pin to AGND with a 1 μF tantalum capacitor and a 100 nF ceramic capacitor. The internal reference cannot be used to drive an external load. 8 SCF Select Calibration Frequency. This logic input selects the frequency on the Calibration Output CF. Table 7 shows calibration frequency selections. 9, 10 S1, S0 Conversion Frequency Logic Input Selection. These logic inputs select one of four possible frequencies for the digital-to-frequency conversion. With this logic input, designers have greater flexibility when designing an energy meter. Table 5 shows conversion frequency selections. 11 RCLKIN On-Chip Clock Enabler. To enable the internal oscillator as a clock source to the chip, a precise low temperature drift resistor at a nominal value of 6.2 kΩ must be connected from this pin to DGND. 12 REVP Negative Power Indicator. This logic output goes high when negative power is detected, such as when the phase angle between the voltage and current signals is greater than 90°. This output is not latched and is reset when positive power is once again detected. The output goes high or low at the same time that a pulse is issued on CF. 13 DGND Digital Ground. This pin provides the ground reference for the digital circuitry in the AD71056, that is, the multiplier, filters, and digital-to-frequency converter. Tie this pin to the digital ground plane of the PCB. The digital ground plane is the ground reference for all digital circuitry, for example, counters (mechanical and digital), MCUs, and indicator LEDs. For accurate noise suppression, connect the analog ground plane to the digital ground plane at one point only—a star ground. 14 CF Calibration Frequency Logic Output. The CF logic output provides instantaneous real power information. This output is for calibration purposes (also see the SCF pin description). 15, 16 F2, F1 Low Frequency Logic Outputs. F1 and F2 supply average real power information. The logic outputs can be used to directly drive electromechanical counters and 2-phase stepper motors. See the Transfer Function section. Rev. A | Page 7 of 20 Document Outline FEATURES GENERAL DESCRIPTION FUNCTIONAL BLOCK DIAGRAM TABLE OF CONTENTS REVISION HISTORY SPECIFICATIONS TIMING CHARACTERISTICS Timing Diagram ABSOLUTE MAXIMUM RATINGS ESD CAUTION TERMINOLOGY PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS THEORY OF OPERATION POWER FACTOR CONSIDERATIONS NONSINUSOIDAL VOLTAGE AND CURRENT APPLICATIONS ANALOG INPUTS Channel V1 (Current Channel) Channel V2 (Voltage Channel) Typical Connection Diagrams POWER SUPPLY MONITOR HPF and Offset Effects Digital-to-Frequency Conversion Connecting to a Microcontroller for Energy Measurement Power Measurement Considerations INTERNAL OSCILLATOR (OSC) TRANSFER FUNCTION Frequency Outputs F1 and F2 Frequency Output CF SELECTING A FREQUENCY FOR AN ENERGY METER APPLICATION Frequency Outputs NO LOAD THRESHOLD NEGATIVE POWER INFORMATION OUTLINE DIMENSIONS ORDERING GUIDE