Datasheet

Data Sheet ADE7758
Rev. E | Page 25 of 72
PGA1
IAP
IAN
IA
ADC
HPF
PGA2
VAP
VN
VA
ADC
60Hz
0.1°
IA
VA
RANGE OF PHASE
CALIBRATION
1111100
60
APHCAL[6:0]
–153.6µs TO +75.6µs
VA
VA ADVANCED BY 4.8µs
(+0.104
° @ 60Hz)
0x7E
IA
60Hz
DIGITAL
INTEGRATOR
ACTIVE AND
REACTIVE
ENERGY
CALCULATION
+1.36°, –2.76° @ 50Hz; 0.022°, 0.043°
+1.63°, –3.31° @ 60Hz; 0.026°, 0.052°
04443-056
Figure 56. Phase Calibration on Voltage Channels
PERIOD MEASUREMENT
The ADE7758 provides the period or frequency measurement
of the line voltage. The period is measured on the phase
specified by Bit 0 to Bit 1 of the MMODE register. The period
register is an unsigned 12-bit FREQ register and is updated
every four periods of the selected phase.
Bit 7 of the LCYCMODE selects whether the period register
displays the frequency or the period. Setting this bit causes the
register to display the period. The default setting is logic low,
which causes the register to display the frequency.
When set to measure the period, the resolution of this register is
96/CLKIN per LSB (9.6 µs/LSB when CLKIN is 10 MHz),
which represents 0.06% when the line frequency is 60 Hz. At
60 Hz, the value of the period register is 1737d. At 50 Hz, the
value of the period register is 2084d. When set to measure
frequency, the value of the period register is approximately 960d at
60 Hz and 800d at 50 Hz. This is equivalent to 0.0625 Hz/LSB.
LINE VOLTAGE SAG DETECTION
The ADE7758 can be programmed to detect when the absolute
value of the line voltage of any phase drops below a certain peak
value for a number of half cycles. Each phase of the voltage
channel is controlled simultaneously. This condition is
illustrated in Figure 57.
Figure 57 shows a line voltage fall below a threshold, which is
set in the SAG level register (SAGLVL[7:0]), for nine half cycles.
Because the SAG cycle register indicates a six half-cycle threshold
(SAGCYC[7:0] = 0x06), the SAG event is recorded at the end of
the sixth half cycle by setting the SAG flag of the corresponding
phase in the interrupt status register (Bit 1 to Bit 3 in the
interrupt status register).
If the SAG enable bit is set to Logic 1 for this phase (Bit 1 to
Bit 3 in the interrupt mask register), the
IRQ
logic output goes
active low (see the section). The phases are compared
to the same parameters defined in the SAGLVL and SAGCYC
registers.
Interrupts
SAGLVL[7:0]
FULL-SCALE
READ RSTATUS
REGISTER
SAGCYC[7:0] = 0x06
6HALFCYCLES
S
AG INTERRUPT FLAG
(BIT 3 TO BIT 5 OF
STATUS REGISTER)
VAP, VBP, OR VCP
SAG EVENT RESET LOW
WHEN VOLTAGE CHANNEL
EXCEEDS SAGLVL[7:0]
04443-057
Figure 57. ADE7758 SAG Detection
Figure 57 shows a line voltage fall below a threshold, which is
set in the SAG level register (SAGLVL[7:0]), for nine half cycles.
Because the SAG cycle register indicates a six half-cycle threshold
(SAGCYC[7:0] = 0x06), the SAG event is recorded at the end of
the sixth half cycle by setting the SAG flag of the corresponding
phase in the interrupt status register (Bit 1 to Bit 3 in the
interrupt status register). If the SAG enable bit is set to Logic 1
for this phase (Bit 1 to Bit 3 in the interrupt mask register), the
IRQ
logic output goes active low (see the section).
The phases are compared to the same parameters defined in the
SAGLVL and SAGCYC registers.
Interrupts