ade7566 Analog Devices, Inc., ade7566 Datasheet - Page 47

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

Line Voltage SAG Detection
In addition to the detection of the loss of the line voltage signal
(zero crossing), the ADE7566/ADE7569 can also be
programmed to detect when the absolute value of the line
voltage drops below a certain peak value for a number of line
cycles. This condition is illustrated in Figure 52.
Figure 52 shows the line voltage falling below a threshold that is
set in the SAG level register (SAGLVL[15:0]) for three line
cycles. The quantities 0 and 1 are not valid for the SAGCYC
register, and the contents represent one more than the desired
number of full line cycles. For example, when the SAG cycle
(SAGCYC[7:0]) contains 0x04, FSAG in the Power Management
Interrupt Flag SFR (IPSMF, 0xF8) is set at the end of the third
line cycle after the line voltage falls below the threshold. If the SAG
enable bit (ESAG) in the Power Management Interrupt Enable SFR
(IPSME, 0xEC) is set, the 8052 core has a pending power supply
monitoring interrupt. The PSM interrupt stays active until the
ESAG bit is cleared (see the Power Supply Monitor Interrupt
(PSM) section).
In Figure 52, the SAG flag (FSAG) is set on the fifth line cycle
after the signal on the voltage channel first dropped below the
threshold level.
SAG Level Set
The 2-byte contents of the SAG level register (SAGLVL, 0x14)
are compared to the absolute value of the output from LPF1.
Therefore, when LPF1 is enabled, writing 0x2038 to the SAG
level register puts the SAG detection level at full scale (see
Figure 52). Writing 0x00 or 0x01 puts the SAG detection level at
0. The SAG level register is compared to the input of the ZX
detection, and detection is made when the contents of the SAG
level register are greater.
Peak Detection
The ADE7566/ADE7569 can also be programmed to detect
when the absolute value of the voltage or current channel
exceeds a specified peak value. Figure 53 illustrates the behavior
of the peak detection for the voltage channel. Both voltage and
current channels are monitored at the same time.
SAGLVL [15:0]
FULL SCALE
SAG FLAG
SAGCYC [7:0] = 0x04
3 LINE CYCLES
Figure 52. SAG Detection
VOLTAGE CHANNEL
SAG RESET LOW
WHEN VOLTAGE
CHANNEL EXCEEDS
SAGLVL [15:0] AND
SAG FLAG RESET
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Figure 53 shows a line voltage exceeding a threshold that is set
in the voltage peak register (VPKLVL[15:0]). The voltage peak
event is recorded by setting the PKV flag in the Interrupt Status
3 SFR (MIRQSTH, 0xDE). If the PKV enable bit is set in the
Interrupt Enable 3 SFR (MIRQENH, 0xDB), the 8052 core has a
pending ADE interrupt. Similarly, the current peak event is
recorded by setting the PKI flag in Interrupt Status 3 SFR
(MIRQSTH, 0xDE). The ADE interrupt stays active until the
PKV or PKI status bit is cleared (see the Energy Measurement
Interrupts section).
Peak Level Set
The contents of the VPKLVL and IPKLVL registers are compared
to the absolute value of the voltage and current channels 2 MSBs,
respectively. Thus, for example, the nominal maximum code
from the current channel ADC with a full-scale signal is
0x28F5C2 (see the Current Channel ADC section). Therefore,
writing 0x28F5 to the IPKLVL register puts the current channel,
peak detection level at full scale and sets the current peak
detection to its least sensitive value. Writing 0x00 puts the
current channel detection level at 0. The detection is done by
comparing the contents of the IPKLVL register to the incoming
current channel sample. The PKI flag indicates that the peak level is
exceeded. If the PKI or PKV bit is set in the Interrupt Enable 3
SFR (MIRQENH, 0xDB), the 8052 core has a pending ADE
interrupt.
Peak Level Record
Each ADE7566/ADE7569 records the maximum absolute value
reached by the voltage and current channels in two different
registers, IPEAK and VPEAK, respectively. Each register is a
24-bit unsigned register that is updated each time the absolute
value of the waveform sample from the corresponding channel
is above the value stored in the VPEAK or IPEAK register. The
contents of the VPEAK register correspond to the maximum
absolute value observed on the voltage channel input. The
contents of IPEAK and VPEAK represent the maximum
absolute value observed on the current and voltage input,
respectively. Reading the RSTVPEAK and RSTIPEAK registers
clears their respective contents after the read operation.
IN MIRQSTH SFR
PKV INTERRUPT
RESET BIT PKV
VPKLVL[15:0]
FLAG
V
2
Figure 53. Peak Level Detection
ADE7566/ADE7569
PKV RESET
LOW WHEN
MIRQSTH SFR
IS READ