ade7566 Analog Devices, Inc., ade7566 Datasheet - Page 63

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

ENERGY-TO-FREQUENCY CONVERSION
The ADE7566/ADE7569 also provide two energy-to-frequency
conversions for calibration purposes. After initial calibration at
manufacturing, the manufacturer or end customer often verify
the energy meter calibration. One convenient way to do this is
for the manufacturer to provide an output frequency that is
proportional to the active power, reactive power, apparent power,
or I
provide a simple, single-wire, optically isolated interface to external
calibration equipment. Figure 73 illustrates the energy-to-
frequency conversion in the ADE7566/ADE7569.
Two digital-to-frequency converters (DFC) are used to generate
the pulsed outputs. When WDIV = 0 or 1, the DFC generates a
pulse each time 1 LSB in the energy register is accumulated. An
output pulse is generated when CFxNUM/CFxDEN number of
pulses are generated at the DFC output. Under steady load
conditions, the output frequency is proportional to the active
power, reactive power, apparent power, or I
CFxSEL bits in the MODE2 register (0x0C).
Both pulse outputs can be enabled or disabled by clearing or
setting Bit DISCF1 and Bit DISCF2 in the MODE1 register
(0x0B), respectively.
Both pulse outputs set separate flags in the Interrupt Status 2 SFR
(MIRQSTM, 0xDD), CF1 and CF2. If the CF1 and CF2 enable
bits in the Interrupt Enable 2 SFR (MIRQENM, 0xDA) are set,
the 8052 core has a pending ADE interrupt. The ADE interrupt
stays active until the CF1 or CF2 status bits are cleared (see the
Energy Measurement Interrupts section).
Pulse Output Configuration
The two pulse output circuits have separate configuration bits
in the MODE2 Register (0x0C. Setting the CFxSEL bits to 0b00,
0b01, or 0b1x configure the DFC to create a pulse output
proportional to active power, to reactive power (not available in
the ADE7566), or to apparent power or I
The selection between I
VARMSCFCON bit in the MODE2 register (0x0C). With this
selection, CF2 cannot be proportional to apparent power if CF1
is proportional to I
apparent power if CF2 is proportional to I
I
VA
rms
rms
VARMSCFCON
under steady load conditions. This output frequency can
MODE2 REGISTER 0x0C
WATT
VAR
Figure 73. Energy-to-Frequency Conversion
CFxSEL[1:0]
rms
, and CF1 cannot be proportional to
rms
and apparent power is done by the
DFC
CFxNUM
CFxDEN
rms
÷
rms
, respectively.
rms
.
, depending on the
CFx PULSE
OUTPUT
Rev. 0 | Page 63 of 136
Pulse Output Characteristic
The pulse output for both DFCs stays low for 90 ms if the pulse
period is longer than 180 ms (5.56 Hz). If the pulse period is
shorter than 180 ms, the duty cycle of the pulse output is 50%.
The pulse output is active low and should preferably be
connected to an LED as shown on Figure 74.
The maximum output frequency with ac input signals at
full scale and CFxNUM = 0x00 and CFxDEN = 0x00 is
approximately 21.1 kHz.
The ADE7566/ADE7569 incorporate two registers per DFC,
CFxNUM[15:0] and CFxDEN[15:0], to set the CFx frequency.
These are unsigned 16-bit registers that can be used to adjust
the CFx frequency to a wide range of values. These frequency
scaling registers are 16-bit registers that can scale the output
frequency by 1/2
If the Value 0 is written to any of these registers, the Value 1
would be applied to the register. The ratio CFxNUM/CFxDEN
should be less than 1 to ensure proper operation. If the ratio of
the CFxNUM/CFxDEN registers is greater than 1, the register
values are adjusted to a ratio of 1. For example, if the output
frequency is 1.562 kHz while the contents of CFxDEN are 0
(0x000), the output frequency can be set to 6.1 Hz by writing
0xFF to the CFxDEN register.
ENERGY REGISTER SCALING
The ADE7566/ADE7569 provide measurements of active,
reactive, and apparent energies that use separate paths and
filtering for calculation. The difference in data paths can result
in small differences in LSB weight between active, reactive, and
apparent energy registers. These measurements are internally
compensated so the scaling is nearly one to one. The relationship
between these registers is shown in Table 45.
Table 45. Energy Registers Scaling
Line Frequency = 50 Hz
VAR = 0.9952 × WATT
VA = 0.9978 × WATT
VAR = 0.9997 × WATT
VA = 0.9977 × WATT
16
to 1 with a step of 1/2
Figure 74. CF Pulse Output
CF
Line Frequency = 60 Hz
VAR = 0.9949 × WATT
VA = 1.0015 × WATT
VAR = 0.9999 × WATT
VA = 1.0015 × WATT
V
DD
ADE7566/ADE7569
16
.
Integrator
Off
Off
On
On