ade7566 Analog Devices, Inc., ade7566 Datasheet - Page 53

• Manufacturer Part Number: ade7566
• Description: Single-phase Energy Measurement Ic With 8052 Mcu, Rtc, And Lcd Driver
• Manufacturer: Analog Devices, Inc.

Figure 61 shows this energy accumulation for full-scale signals
(sinusoidal) on the analog inputs. The three displayed curves
illustrate the minimum period of time it takes the energy register
to roll over when the active power gain register contents are
0x7FF, 0x000, and 0x800. The watt gain register is used to carry
out power calibration in the ADE7566/ADE7569. As shown, the
fastest integration time occurs when the watt gain register is set
to maximum full scale, that is, 0x7FF.
0x7F,FFFF
0x3F,FFFF
Note that the energy register contents roll over to full-scale
negative (0x800000) and continue to increase in value when the
power or energy flow is positive (see Figure 61). Conversely, if
the power is negative, the energy register underflows to full-
scale positive (0x7FFFFF) and continues to decrease in value.
By using the interrupt enable register, the ADE7566/ADE7569
can be configured to issue an ADE interrupt to the 8052 core
when the active energy register is half-full (positive or negative)
or when an overflow or underflow occurs.
Integration Time under Steady Load
As mentioned in the Active Energy Calculation section, the
discrete time sample period (T) for the accumulation register is
1.22 μs (5/CLKIN). With full-scale sinusoidal signals on the
analog inputs and the WGAIN register set to 0x000, the average
word value from each LPF2 is 0xCCCCD (see Figure 58). The
maximum positive value that can be stored in the internal
49-bit register is 2
The integration time under these conditions when WDIV = 0 is
calculated in the following equation:
When WDIV is set to a value different than 0, the integration
time varies, as shown in Equation 14.
0x00,0000
0x40,0000
0x80,0000
WATTHR[23:0]
Time =
Time = Time
0
Figure 61. Energy Register Rollover Time for Full-Scale Power
xFFFF,
0
xCCCCD
3.41
FFFF,
(Minimum and Maximum Power Gain)
6.82
WDIV = 0
48
(or 0xFFFF,FFFF,FFFF) before it overflows.
FFFF
10.2
× WDIV
×
. 1
22
μ
s
13.7
=
409
6 .
sec
TIME (Minutes)
=
. 6
WGAIN = 0x7FF
WGAIN = 0x000
WGAIN = 0x800
82
min
Rev. 0 | Page 53 of 136
(13)
(14)
Active Energy Accumulation Modes
Watt Signed Accumulation Mode
The ADE7566/ADE7569 active energy default accumulation
mode is a watt-signed accumulation based on the active power
information.
Watt Positive-Only Accumulation Mode
The ADE7566/ADE7569 are placed in watt positive-only
accumulation mode by setting the POAM bit in the ACCMODE
register (0x0F). In this mode, the energy accumulation is only
done for positive power, ignoring any occurrence of negative
power above or below the no-load threshold (see Figure 62).
The CF pulse also reflects this accumulation method when in
this mode. The default setting for this mode is off. Detection of
the transitions in the direction of power flow and detection of
no-load threshold are active in this mode.
Watt Absolute Accumulation Mode
The ADE7566/ADE7569 are placed in watt absolute accumula-
tion mode by setting the ABSAM bit in the ACCMODE register
(0x0F). In this mode, the energy accumulation is done using the
absolute active power, ignoring any occurrence of power below
the no-load threshold (see Figure 63). The CF pulse also reflects
this accumulation method when in this mode. The default
setting for this mode is off. Detection of the transitions in the
direction of power flow, and detection of no-load threshold are
active in this mode.
Figure 62. Energy Accumulation in Positive-Only Accumulation Mode
ACTIVE ENERGY
ACTIVE POWER
APSIGN FLAG
THRESHOLD
THRESHOLD
NO-LOAD
NO-LOAD
INTERRUPT STATUS REGISTERS
POS
ADE7566/ADE7569
NEG
POS