ADE7758ARW Analog Devices Inc, ADE7758ARW Datasheet - Page 27

• Manufacturer Part Number: ADE7758ARW
• Description: IC ENERGY METERING 24-SOIC
• Manufacturer: Analog Devices Inc

Specifications of ADE7758ARW

• Rohs Status: RoHS non-compliant
• Input Impedance: 380 KOhm
• Measurement Error: 0.1%
• Voltage - I/o High: 2.4V
• Voltage - I/o Low: 0.8V
• Current - Supply: 8mA
• Voltage - Supply: 4.75 V ~ 5.25 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-SOIC (0.300", 7.50mm Width)
• Meter Type: 3 Phase
• Lead Free Status / RoHS Status: Not Compliant

WAVEFORMS
WAVEFORMS
PHASE SEQUENCE DETECTION
The ADE7758 has an on-chip phase sequence error detection
interrupt. If the zero crossing of Phase A is not followed by
Phase C but by Phase B, the SEQERR bit (Bit 19) in the STATUS
register is set. If SEQERR is set in the mask register, the IRQ
logic output goes active low (see the
depicts how the interrupt is issued in two different
configurations.
Note that if it is desired to have the interrupt occur when
Phase A is followed by Phase B and not Phase C, then the analog
inputs for Phase C and Phase B should be swapped. In this case,
the Phase B voltage input should be wired to the VCP pin and
the Phase C voltage input should be wired to the VBP pin.
POWER-SUPPLY MONITOR
The ADE7758 also contains an on-chip power-supply monitor.
The analog supply (AVDD) is monitored continuously by the
ADE7758. If the supply is less than 4 V ± 5%, the ADE7758
goes into an inactive state, that is, no energy is accumulated
when the supply voltage is below 4 V. 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.
This gives a high degree of immunity to false triggering due to
noisy supplies. Figure 61 shows the behavior of the ADE7758
when the voltage of AVDD falls below the power-supply
monitor threshold. The power supply and decoupling for the
part should be designed such that the ripple at AVDD does not
exceed 5 V ± 5% as specified for normal operation.
CROSSINGS
CROSSINGS
VOLTAGE
VOLTAGE
ZERO
ZERO
A
A
A = 0°
A = 0°
C
SEQERR BIT OF STATUS REGISTER IS NOT SET
B
SEQERR BIT OF STATUS REGISTER IS SET
Figure 60. Phase Sequence Detection
B
C
B = –120°
C = –120°
A
A
C
B
C = +120°
B = +120°
B
C
Interrupts
A
A
C
B
section).
C
B
Figure 60
A
A
C
B
Rev. D | Page 27 of 72
CALCULATIONS
REFERENCE CIRCUIT
The nominal reference voltage at the REF
This is the reference voltage used for the ADCs in the
ADE7758. However, the current channels have three input
range selections (full scale is selectable among 0.5 V, 0.25 V, and
0.125 V). This is achieved by dividing the reference internally
by 1, ½, and ¼. The reference value is used for the ADC in the
current channels. Note that the full-scale selection is only
available for the current inputs.
The REF
example, an external 2.5 V reference. Note that the nominal
reference value supplied to the ADC is now 2.5 V and not
2.42 V. This has the effect of increasing the nominal analog
input signal range by 2.5/2.42 × 100% = 3% or from 0.5 V to
0.5165 V.
The voltage of the ADE7758 reference drifts slightly with
temperature; see the Specifications section for the temperature
coefficient specification (in ppm/°C). The value of the temperature
drift varies from part to part. Because the reference is used for
all ADCs, any x% drift in the reference results in a 2x%
deviation of the meter accuracy. The reference drift resulting
from temperature changes is usually very small and typically
much smaller than the drift of other components on a meter.
Alternatively, the meter can be calibrated at multiple temperatures.
INTERNAL
ADE7758
AV
IN/OUT
DD
5V
4V
0V
Figure 61. On-Chip, Power-Supply Monitoring
INACTIVE
pin can be overdriven by an external source, for
ACTIVE
TIME
IN/OUT
INACTIVE
pin is 2.42 V.
ADE7758