AD71056

Rev. A | Page 7 of 20

PIN CONFIGURATION AND FUNCTION DESCRIPTIONS

F1

16

F2

15

CF

14

DGND

13

REVP

12

RCLKIN

11

S0

10

S1

9

AD71056

TOP VIEW

(Not to Scale)

Figure 3. Pin Configuration

Table 4. Pin Function Descriptions

Pin No.

Mnemonic

Description

1

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

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.