ADE7761B

Rev. 0 | Page 12 of 24

Typical Connection Diagrams

Figure 15 shows a typical connection diagram for Channel V1.

The analog inputs are used to monitor both the phase and

neutral currents. Because of the large potential difference

between the phase and neutral, two current transformers (CTs)

must be used to provide the isolation. Note that both CTs are

referenced to analog ground (AGND); therefore, the common-

mode voltage is 0 V. The CT turn ratio and burden resistor (RB)

are selected to give a peak differential voltage of ±660 mV/gain.

AGND

CT

CT

RB

RB

IN

IP

±660mV

GAIN

±660mV

GAIN

Figure 15. Typical Connection for Channel V1

Figure 16 shows two typical connections for Channel V2.

The first option uses a potential transformer (PT) to provide

complete isolation from the main voltage. In the second option,

the ADE7761B is biased around the neutral wire, and a resistor

divider is used to provide a voltage signal that is proportional to

the line voltage. Adjusting the ratio of RA and RB + VR is a

convenient way to carry out a gain calibration on the meter.

±660mV

AGND

Figure 16. Typical Connections for Channel V2

Figure 17 shows a typical connection for the MISCAL input.

to set the MISCAL voltage.

VR1

RD

RC

MISCAL

Figure 17. Typical Connection for MISCAL

Adjusting the level of MISCAL to calibrate the meter in missing

neutral mode can be done by changing the ratio of RC and

RD + VR1. When the internal reference is used, the values of RC,

RD, and VR1 must be chosen to limit the current sourced by

the internal reference sourcing current to below the specified

VR1 > 600 kΩ.

INTERNAL OSCILLATOR

The nominal internal oscillator frequency is 450 kHz when

between RCLKIN and DGND (see Figure 18).

2.5V

REFERENCE

INTERNAL

OSCILLATOR

9

ADE7761B

DGND

RCLKIN

3kΩ

14

17

Figure 18. Internal Oscillator Connection

The internal oscillator frequency is inversely proportional to the

value of this resistor. Although the internal oscillator operates

it is recommended that a value be chosen within the range of

the nominal value.

The output frequencies on CF, F1, and F2 are directly propor-

must have a low tolerance and low temperature drift. A low

tolerance resistor limits the variation of the internal oscillator

frequency. A small variation of the clock frequency and, conse-

quently, of the output frequencies from meter to meter contributes

to a smaller calibration range of the meter.

A low temperature drift resistor directly limits the variation of

the internal clock frequency over temperature. The stability of

the meter to external variation is then better ensured by design.