Energy Metering IC with Integrated

Oscillator and Positive Power Accumulation

ADE7768

Rev. A

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FEATURES

On-chip oscillator as clock source

High accuracy, supports 50 Hz/60 Hz IEC62053-21

Less than 0.1% error over a dynamic range of 500 to 1

Supplies positive-only average real power on frequency

outputs F1 and F2

High frequency output CF calibrates and supplies

instantaneous, positive-only real power

Logic output REVP indicates potential miswiring or negative

power

Direct drive for electromechanical counters and 2-phase

stepper motors (F1 and F2)

Proprietary ADCs and DSPs provide high accuracy over

large variations in environmental conditions and time

On-chip power supply monitoring

On-chip creep protection (no-load threshold)

On-chip reference 2.45 V (20 ppm/°C typical) with

external overdrive capability

Single 5 V supply, low power (20 mW typical)

Low cost CMOS process

GENERAL DESCRIPTION

It is a pin reduction version of the ADE7755, enhanced with a

precise oscillator circuit that serves as a clock source to the chip.

The ADE7768 eliminates the cost of an external crystal or

resonator, thus reducing the overall cost of a meter built with

this IC. The chip directly interfaces with the shunt resistor.

The ADE7768 specifications surpass the accuracy require-

ments of the IEC62053-21 standard. The AN-679 Application

Note can be used as a basis for a description of an IEC61036

(equivalent to IEC62053-21) low cost, watt-hour meter

reference design.

The only analog circuitry used in the ADE7768 is in the Σ-Δ

ADCs and reference circuit. All other signal processing, such as

multiplication and filtering, is carried out in the digital domain.

This approach provides superior stability and accuracy over

time and extreme environmental conditions.

The ADE7768 supplies positive-only average real power

information on the low frequency outputs, F1 and F2. These

outputs can be used to directly drive an electromechanical

counter or interface with an MCU. The high frequency CF logic

output, ideal for calibration purposes, provides instantaneous

positive-only, real power information.

The ADE7768 includes a power supply monitoring circuit on

falls below 4 V, the ADE7768 also remains inactive and the F1,

F2, and CF outputs are in their nonactive modes.

Internal phase matching circuitry ensures that the voltage and

current channels are phase matched, while the HPF in the

current channel eliminates dc offsets. An internal no-load

threshold ensures that the ADE7768 does not exhibit creep

when no load is present. When REVP is logic high, the

ADE7768 does not generate any pulse on F1, F2, and CF.

The ADE7768 comes in a 16-lead, narrow body SOIC package.

FUNCTIONAL BLOCK DIAGRAM

MULTIPLIER

REVP

V2P

V2N

V1P

RCLKIN

F1

F2

CF

SCF

S0

S1

PHASE

CORRECTION

4k

Ω

...110101...

SIGNAL

PROCESSING

BLOCK

POWER

SUPPLY MONITOR

Σ-Δ

ADC

V1N

ADE7768

...11011001...

2.5V

REFERENCE

AGND

DGND

Φ

INTERNAL

OSCILLATOR

Σ-Δ

ADC

LPF

HPF

+

+

1

6

13

7

11

8

10

12

14

16

15

9

DIGITAL-TO-FREQUENCY

CONVERTER

2

3

4

5

Figure 1.