ANALOG DEVICES ADE7755 Service Manual

Energy Metering IC with Pulse Output

FEATURES

High accuracy, surpasses 50 Hz/60 Hz IEC 687/IEC 1036 Less than 0.1% error over a dynamic range of 500 to 1 Supplies active power on the frequency outputs, F1 and F2 High frequency output CF is intended for calibration and

supplies instantaneous active power Synchronous CF and F1/F2 outputs Logic output REVP provides information regarding the sign

of the active power Direct drive for electromechanical counters and 2-phase

stepper motors (F1 and F2) Programmable gain amplifier (PGA) in the current channel

facilitates usage of small shunts and burden resistors 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 2.5 V ± 8% (30 ppm/°C typical) with

external overdrive capability Single 5 V supply, low power (15 mW typical) Low cost CMOS process

ADE7755

GENERAL DESCRIPTION

The ADE7755 is a high accuracy electrical energy measurement IC. The part specifications surpass the accuracy requirements as quoted in the IEC 1036 standard.

The only analog circuitry used in the ADE7755 is in the ADCs and reference circuit. All other signal processing (for example, multiplication and filtering) is carried out in the digital domain. This approach provides superior stability and accuracy over extremes in environmental conditions and over time.

The ADE7755 supplies average active power information on the low frequency outputs, F1 and F2. These logic outputs can be used to directly drive an electromechanical counter or interface to an MCU. The CF logic output gives instantaneous active power information. This output is intended to be used for calibration purposes or for interfacing to an MCU.

The ADE7755 includes a power supply monitoring circuit on the AV

supply pin. The ADE7755 remains in a reset condition until

the supply voltage on AV 4 V, the ADE7755 resets and no pulse is issued on F1, F2, and CF.

Internal phase matching circuitry ensures that the voltage and current channels are phase matched whether the HPF in Channel 1 is on or off. An internal no load threshold ensures that the ADE7755 does not exhibit any creep when there is no load.

The ADE7755 is available in a 24-lead SSOP package.

reaches 4 V. If the supply falls below

FUNCTIONAL BLOCK DIAGRAM

G0 G1

V1P

V1N

V2P

V2N

REFERENCE

×1, ×2, ×8, ×16

2.5V

U.S. Patents 5,745,323; 5,760,617; 5,862,069; and 5,872,469.

Rev. A

Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners.

POWER

SUPPLY MONITOR

PGA

ADC

4kΩ

IN/OUT

AGND

...110101. ..

...11011001. ..

ADE7755

CORRECTION

PHASE

MULTIPLIER

Figure 1.

DCAC/

HPF

DIGITAL -TO-FREQUENCY

CONVERTER

DGND

PROCESSING

LPF

21121131516

SIGNAL

BLOCK

242220131412181710

RESET

F2F1CFREVPS1S0SCFCLKOUTCLKINREF

02896-001

ADE7755

Features .............................................................................................. 1

General Description ......................................................................... 1

Functional Block Diagram .............................................................. 1

Revision History ............................................................................... 2

Specifications ..................................................................................... 3

Timing Characteristics ................................................................ 4

Absolute Maximum Ratings ............................................................ 5

ESD Caution .................................................................................. 5

Pin Configuration and Function Descriptions ............................. 6

Typical Performance Characteristics ............................................. 8

Terminology .................................................................................... 11

Theory of Operation ...................................................................... 12

Power Factor Considerations .................................................... 12

Nonsinusoidal Voltage and Current ........................................ 13

Analog Inputs ............................................................................. 13

Typical Connection Diagrams .................................................. 14

Power Supply Monitor ............................................................... 14

Digital-to-Frequency Conversion ............................................ 15

Interfacing the ADE7755 to a Microcontroller for Energy

Measurement ............................................................................... 16

Power Measurement Considerations ....................................... 16

Transfer Function ....................................................................... 17

Selecting a Frequency for an Energy Meter Application ...... 18

Frequency Outputs ..................................................................... 18

No Load Threshold .................................................................... 19

Outline Dimensions ....................................................................... 20

Ordering Guide .......................................................................... 20



REVISION HISTORY

8/09—Rev. 0 to Rev. A

Changes to Format ............................................................. Universal

Changes to Features Section and General Description Section . 1

Moved Figure 2 ................................................................................. 4

Changes to Pin 22, Pin 23, and Pin 24 Descriptions, Table 4 ..... 7

Changes to Terminology Section.................................................. 11

Changes to Theory of Operation Section, Figure 22, Power

Factor Considerations Section, and Figure 23 ............................ 12

Changes to Nonsinusoidal Voltage and Current Section and

Analog Inputs Section .................................................................... 13

Changes to Figure 27 ...................................................................... 14

Changes to HPF and Offset Effects Section, Figure 29, and

Digital-to-Frequency Conversion Section .................................. 15

Changes to Figure 32 ...................................................................... 16

Changes to Transfer Function Section ......................................... 17

Changes to Selecting a Frequency for an Energy Meter

Application Section ........................................................................ 18

Changes to No Load Threshold Section ...................................... 19

Updated Outline Dimensions ....................................................... 20

Changes to Ordering Guide .......................................................... 20

5/02—Revision 0: Initial Version

Rev. A | Page 2 of 20

ADE7755

SPECIFICATIONS

AVDD = DVDD = 5 V ± 5%, AGND = DGND = 0 V, on-chip reference, CLKIN = 3.58 MHz, T

Table 1.

Parameter Min Typ Max Unit Test Conditions/Comments

ACCURACY

1, 2

Measurement Error1 on Channel 1 Channel 2 with full-scale signal (±660 mV), 25°C

Gain = 1 0.1 % reading Over a dynamic range of 500 to 1 Gain = 2 0.1 % reading Over a dynamic range of 500 to 1 Gain = 8 0.1 % reading Over a dynamic range of 500 to 1 Gain = 16 0.1 % reading Over a dynamic range of 500 to 1

Phase Error1 Between Channels Line frequency = 45 Hz to 65 Hz

V1 Phase Lead 37° (PF = 0.8 Capacitive) ±0.1 Degrees V1 Phase Lag 60° (PF = 0.5 Inductive) ±0.1 Degrees

AC Power Supply Rejection

Output Frequency Variation (CF) 0.2 % reading

AC/DC AC/DC AC/DC V1 = 100 mV rms, V2 = 100 mV rms @ 50 Hz,

ripple on AV

DC Power Supply Rejection

Output Frequency Variation (CF) ±0.3 % reading

AC/DC V1 = 100 mV rms, V2 = 100 mV rms,

AVDD = DVDD = 5 V ± 250 mV

ANALOG INPUTS See the Analog Inputs section

Maximum Signal Levels ±1 V V1P, V1N, V2N, and V2P to AGND Input Impedance (DC) 390 kΩ CLKIN = 3.58 MHz

−3 dB Bandwidth 14 kHz CLKIN/256, CLKIN = 3.58 MHz ADC Offset Error Gain Error

1, 2

±25 mV Gain = 1

±7 % ideal External 2.5 V reference, gain = 1

V1 = 470 mV dc, V2 = 660 mV dc Gain Error Match

±0.2 % ideal External 2.5 V reference

REFERENCE INPUT

REF

Input Voltage Range 2.7 V 2.5 V + 8%

IN/OUT

2.3 V 2.5 V − 8% Input Impedance 3.2 kΩ Input Capacitance 10 pF

ON-CHIP REFERENCE Nominal 2.5 V

Reference Error ±200 mV Temperature Coefficient ±30 ppm/°C

CLKIN Note all specifications for CLKIN of 3.58 MHz

Input Clock Frequency 4 MHz 1 MHz LOGIC INPUTS3

SCF, S0, S1, AC/DC, RESET, G0, and G1

Input High Voltage, V Input Low Voltage, V

2.4 V DVDD = 5 V ± 5%

INH

0.8 V DVDD = 5 V ± 5%

INL

Input Current, IIN ±3 μA Typically 10 nA, VIN = 0 V to DVDD Input Capacitance, CIN 10 pF

LOGIC OUTPUTS3

F1 and F2

Output High Voltage, VOH 4.5 V I Output Low Voltage, VOL 0.5 V I

SOURCE

SINK

CF and REVP

Output High Voltage, VOH 4 V I Output Low Voltage, VOL 0.5 V I

SOURCE

SINK

to T

MIN

= −40°C to +85°C.

MAX

= 0 and AC/DC = 1 = 0 and AC/DC = 1 = 1, S0 = S1 = 1, G0 = G1 = 0

of 200 mV rms @ 100 Hz

= 1, S0 = S1 = 1, G0 = G1 = 0

1, 2

= 10 mA, DVDD = 5 V

= 5 mA, DVDD = 5 V

Rev. A | Page 3 of 20

ADE7755

Parameter Min Typ Max Unit Test Conditions/Comments

POWER SUPPLY For specified performance

AVDD 4.75 V 5 V − 5%

5.25 V 5 V + 5% DVDD 4.75 V 5 V − 5%

5.25 V 5 V + 5% AIDD 3 mA Typically 2 mA DIDD 2.5 mA Typically 1.5 mA

See the Terminology section.

See the Typical Performance Characteristics section for the plots.

Sample tested during initial release and after any redesign or process change that may affect this parameter.

TIMING CHARACTERISTICS

AVDD = DVDD = 5 V ± 5%, AGND = DGND = 0 V, on-chip reference, CLKIN = 3.58 MHz, T

MIN

to T

= −40°C to +85°C.

MAX

Table 2.

Parameter

275 ms F1 and F2 pulse width (logic low)

1, 2

Specification Unit Test Conditions/Comments

t2 See Tabl e 7 sec Output pulse period; see the Transfer Function section t3 1/2 t2 sec Time between F1 falling edge and F2 falling edge

3, 4

90 ms CF pulse width (logic high)

t5 See Tabl e 8 sec CF pulse period; see the Transfer Function section t6 CLKIN/4 sec Minimum time between F1 and F2 pulse

Sample tested during initial release and after any redesign or process change that may affect this parameter.

See Figure 2.

The pulse widths of F1, F2, and CF are not fixed for higher output frequencies. See the Frequency Outputs section.

The CF pulse is always 18 μs in the high frequency mode. See the Frequency Outputs section and Table 8.

2896-002

Figure 2. Timing Diagram for Frequency Outputs

Rev. A | Page 4 of 20

ADE7755

ABSOLUTE MAXIMUM RATINGS

TA = 25°C, unless otherwise noted.

Table 3.

Parameter Rating

AVDD to AGND −0.3 V to +7 V DVDD to DGND −0.3 V to +7 V DV

to AVDD −0.3 V to +0.3 V

Analog Input Voltage to AGND

V1P, V1N, V2P, and V2N −6 V to +6 V Reference Input Voltage to AGND −0.3 V to AVDD + 0.3 V Digital Input Voltage to DGND −0.3 V to DVDD + 0.3 V Digital Output Voltage to DGND −0.3 V to DVDD + 0.3 V Operating Temperature Range

Industrial −40°C to +85°C Storage Temperature Range −65°C to +150°C Junction Temperature 150°C 24-Lead SSOP, Power Dissipation 450 mW

θJA Thermal Impedance 112°C/W

Lead Temperature, Soldering

Vapor Phase (60 sec) 215°C Infrared (15 sec) 220°C

Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

ESD CAUTION

Rev. A | Page 5 of 20

ADE7755

PIN CONFIGURATION AND FUNCTION DESCRIPTIONS

Table 4. Pin Function Descriptions

Pin No. Mnemonic Description

1 DVDD

Digital Power Supply. This pin provides the supply voltage for the digital circuitry in the ADE7755. The supply voltage should be maintained at 5 V ± 5% for specified operation. This pin should be decoupled with a 10 μF capacitor in parallel with a ceramic 100 nF capacitor.

High-Pass Filter Select. This logic input is used to enable the HPF in Channel 1 (current channel). A Logic 1 on

AC/DC

this pin enables the HPF. The associated phase response of this filter is internally compensated over a frequency range of 45 Hz to 1 kHz. The HPF should be enabled in power metering applications.

3 AVDD

Analog Power Supply. This pin provides the supply voltage for the analog circuitry in the ADE7755. The supply should be maintained at 5 V ± 5% for specified operation. Every effort should be made to minimize power supply ripple and noise at this pin by the use of proper decoupling. This pin should be decoupled to AGND

with a 10 μF capacitor in parallel with a ceramic 100 nF capacitor. 4, 19 NC No Connect. 5, 6 V1P, V1N

Analog Inputs for Channel 1 (Current Channel). These inputs are fully differential voltage inputs with a

maximum differential signal level of ±470 mV for specified operation. Channel 1 also has a PGA, and the gain

selections are outlined in Tab le 5. The maximum signal level at these pins is ±1 V with respect to AGND. Both

inputs have internal ESD protection circuitry. An overvoltage of ±6 V can be sustained on these inputs without

risk of permanent damage. 7, 8 V2N, V2P

Negative and Positive Inputs for Channel 2 (Voltage Channel). These inputs provide a fully differential input pair

with a maximum differential input voltage of ±660 mV for specified operation. The maximum signal level at

these pins is ±1 V with respect to AGND. Both inputs have internal ESD protection circuitry, and an overvoltage

of ±6 V can be sustained on these inputs without risk of permanent damage. 9

Reset Pin. A logic low on this pin holds the ADCs and digital circuitry in a reset condition.

RESET

Bringing this pin logic low clears the ADE7755 internal registers. 10 REF

IN/OUT

This pin provides access to the on-chip voltage reference. The on-chip reference has a nominal value of

2.5 V ± 8% and a typical temperature coefficient of 30 ppm/°C. An external reference source may also be

connected at this pin. In either case, this pin should be decoupled to AGND with a 1 μF ceramic capacitor and

a 100 nF ceramic capacitor. 11 AGND

This pin provides the ground reference for the analog circuitry in the ADE7755, that is, the ADCs and reference.

This pin should be tied to the analog ground plane of the PCB. The analog ground plane is the ground reference

for all analog circuitry, for example, antialiasing filters and current and voltage transducers. For good noise

suppression, the analog ground plane should be connected to the digital ground plane at one point only. A

star ground configuration helps to keep noisy digital currents away from the analog circuits. 12 SCF

Select Calibration Frequency. This logic input is used to select the frequency on the calibration output, CF.

Tab le 8 shows how the calibration frequencies are selected. 13, 14 S1, S0

These logic inputs are used to select one of four possible frequencies for the digital-to-frequency conversion.

This offers the designer greater flexibility when designing the energy meter. See the Selecting a Frequency for

an Energy Meter Application section. 15, 16 G1, G0

These logic inputs are used to select one of four possible gains for Channel 1, that is, V1. The possible gains

are 1, 2, 8, and 16. See the Analog Inputs section.

AC/DC

V1P

V1N

V2N

V2P

RESET

IN/OUT

AGND

SCF

NC = NO CONNECT

REF

Figure 3. Pin Configuration

ADE7755

TOP VIEW

(Not to Scale)

DGND

REVP

CLKOUT

CLKIN

02896-003

Rev. A | Page 6 of 20

+ 14 hidden pages

ANALOG DEVICES ADE7755 Service Manual

FEATURES

GENERAL DESCRIPTION

FUNCTIONAL BLOCK DIAGRAM

TABLE OF CONTENTS

REVISION HISTORY

SPECIFICATIONS

TIMING CHARACTERISTICS

ABSOLUTE MAXIMUM RATINGS

ESD CAUTION

PIN CONFIGURATION AND FUNCTION DESCRIPTIONS