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ADE7761A

Energy Metering IC with On-Chip Fault and Missing Neutral Detection

Analog Devices 

OPERATION

POWER SUPPLY MONITOR

The ADE7761A continuously monitors the power supply (VDD)

with its on-chip, power supply monitor. If the supply is less than

4 V ± 5%, the ADE7761A goes into an inactive state, that is, no

energy is accumulated and the CF, F1, and F2 outputs are

disabled. This is useful to ensure correct device operation at

power-up and during power-down. The power supply monitor

has built-in hysteresis and filtering, which provides a high

degree of immunity to false triggering due to noisy supplies.

The power supply and decoupling for the part should be such

that the ripple at VDD does not exceed 5 V ± 5% as specified for

normal operation.

VDD

5V

4V

0V

TIME

ADE7761A

REVP - FAULT - CF - INACTIVE

F1 - F2 OUTPUTS

ACTIVE

INACTIVE

Figure 11. On-Chip, Power Supply Monitoring

ANALOG INPUTS

Channel V1 (Current Channel)

The voltage outputs from the current transducers are connected

to the ADE7761A at Channel V1. It has two voltage inputs, V1A

and V1B. These inputs are fully differential with respect to V1N.

However, at any one time, only one is selected to perform the

power calculation (see the Fault Detection section).

The maximum peak differential signal on V1A − V1N and V1B − V1N

is ±660 mV. However, Channel 1 has a programmable gain

amplifier (PGA) with user-selectable gains of 1 or 16 (see

Table 5). This gain facilitates easy transducer interfacing.

Table 5. Channel 1 Dynamic Range

PGA

Gain

Maximum Differential Signal (mV)

0

1

660

1

16

41

Figure 12 shows the maximum signal levels on V1A, V1B, and

V1N. The maximum differential voltage is ±660 mV divided by

the gain selection. The differential voltage signal on the inputs

must be referenced to a common mode (usually AGND).

ADE7761A

V1A, V1B

+660mV

GAIN

+

VCM

VCM

–660mV

GAIN

+ VCM

DIFFERENTIAL INPUT A

±660mV MAX PEAK

COMMON MODE

±100mV MAX

VCM

AGND

DIFFERENTIAL INPUT B

±660mV MAX PEAK

V1A

V1

V1N

V1

V1B

Figure 12. Maximum Signal Levels, Channel 1

Channel V2 (Voltage Channel)

The output of the line voltage transducer is connected to the

ADE7761A at this analog input. Channel V2 is a single-ended,

voltage input. The maximum peak differential signal on Channel 2

is ±660 mV with respect to V2N. Figure 13 shows the maximum

signal levels that can be connected to Channel 2.

V2

+660mV + VCM

VCM

DIFFERENTIAL INPUT

±660mV MAX PEAK

V2P

V2

V2N

–660mV + VCM

COMMON MODE VCM

±100mV MAX

Figure 13. Maximum Signal Levels, Channel 2

The differential voltage V2P − V2N must be referenced to a

common mode (usually AGND). The analog inputs of the

ADE7761A can be driven with common-mode voltages of up

to 100 mV with respect to AGND. However, the best results

are achieved using a common mode equal to AGND.

MISCAL Input

The input for the power calibration in missing neutral mode

is connected to the ADE7761A at this analog input. MISCAL is

a single-ended, voltage input. It is recommended to use a dc

signal derived from the voltage reference to drive this pin. The

maximum peak differential signal on MISCAL is 660 mV with

respect to V2N. Figure 14 shows the maximum signal levels that

can be connected to the MISCAL pin.

MISCAL

+660mV + VCM

VCM

DIFFERENTIAL INPUT

±660mV MAX PEAK

COMMON MODE

±100mV MAX

MISCAL

MISCAL

V2N

VCM

AGND

Figure 14. Maximum Signal Levels, MISCAL

Rev. 0 | Page 11 of 24

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