ADE7753 Ver la hoja de datos (PDF) - Analog Devices
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ADE7753 Datasheet PDF : 60 Pages
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ADE7753
THEORY OF OPERATION
ANALOG INPUTS
The ADE7753 has two fully differential voltage input channels.
The maximum differential input voltage for input pairs V1P/V1N
and V2P/V2N is ±0.5 V. In addition, the maximum signal level
on analog inputs for V1P/V1N and V2P/ V2N is ±0.5 V with
respect to AGND.
Each analog input channel has a programmable gain amplifier
(PGA) with possible gain selections of 1, 2, 4, 8, and 16. The
gain selections are made by writing to the gain register—see
Figure 32. Bits 0 to 2 select the gain for the PGA in Channel 1,
and the gain selection for the PGA in Channel 2 is made via
Bits 5 to 7. Figure 31 shows how a gain selection for Channel 1
is made using the gain register.
GAIN[7:0]
76 5 4 3 2 1 0
00 0 0 0 0 0 0
GAIN (K)
SELECTION
V1P
VIN
K × VIN
V1N
+
76 5 4 3 2 1 0
OFFSET ADJUST
(±50mV)
00 0 0 0 0 0 0
CH1OS[7:0]
BITS 0 to 5: SIGN MAGNITUDE CODED OFFSET CORRECTION
BIT 6: NOT USED
BIT 7: DIGITAL INTEGRATOR (ON = 1, OFF = 0; DEFAULT OFF)
02875-0-031
Figure 31. PGA in Channel 1
In addition to the PGA, Channel 1 also has a full-scale input
range selection for the ADC. The ADC analog input range
selection is also made using the gain register—see Figure 32. As
mentioned previously, the maximum differential input voltage
is 0.5 V. However, by using Bits 3 and 4 in the gain register, the
maximum ADC input voltage can be set to 0.5 V, 0.25 V, or
0.125 V. This is achieved by adjusting the ADC reference—see
the ADE7753 Reference Circuit section. Table 5 summarizes the
maximum differential input signal level on Channel 1 for the
various ADC range and gain selections.
Table 5. Maximum Input Signal Levels for Channel 1
Max Signal
ADC Input Range Selection
Channel 1
0.5 V
0.25 V
0.125 V
0.5 V
Gain = 1
−
−
0.25 V
Gain = 2
Gain = 1
−
0.125 V
Gain = 4
Gain = 2
Gain = 1
0.0625 V
Gain = 8
Gain = 4
Gain = 2
0.0313 V
Gain = 16
Gain = 8
Gain = 4
0.0156 V
−
Gain = 16
Gain = 8
0.00781 V
−
−
Gain = 16
GAIN REGISTER*
CHANNEL 1 AND CHANNEL 2 PGA CONTROL
76 54 32 10
00
00
00
0 0 ADDR:
0x0F
PGA 2 GAIN SELECT
PGA 1 GAIN SELECT
000 = × 1
000 = × 1
001 = × 2
001 = × 2
010 = × 4
010 = × 4
011 = × 8
011 = × 8
100 = × 16
100 = × 16
CHANNEL 1 FULL-SCALE SELECT
* REGISTER CONTENTS
SHOW POWER-ON DEFAULTS
00 = 0.5V
01 = 0.25V
10 = 0.125V
02875-0-032
Figure 32. ADE7753 Analog Gain Register
It is also possible to adjust offset errors on Channel 1 and
Channel 2 by writing to the offset correction registers, CH1OS
and CH2OS, respectively. These registers allow channel offsets
in the range ±20 mV to ±50 mV (depending on the gain setting)
to be removed. Channel 1 and 2 offset registers are sign magni-
tude coded. A negative number is applied to the Channel 1
offset register, CH1OS, for a negative offset adjustment. Note
that the Channel 2 offset register is inverted. A negative number
is applied to CH2OS for a positive offset adjustment. It is not
necessary to perform an offset correction in an energy measure-
ment application if HPF in Channel 1 is switched on. Figure 33
shows the effect of offsets on the real power calculation. As seen
from Figure 33, an offset on Channel 1 and Channel 2
contributes a dc component after multiplication. Because this dc
component is extracted by LPF2 to generate the active (real)
power information, the offsets contribute an error to the active
power calculation. This problem is easily avoided by enabling
HPF in Channel 1. By removing the offset from at least one
channel, no error component is generated at dc by the
multiplication. Error terms at cos(ωt) are removed by LPF2 and
by integration of the active power signal in the active energy
register (AENERGY[23:0]) —see the Energy Calculation section.
Rev. C | Page 16 of 60
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