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EVAL-ADE7759E Datasheet PDF : 32 Pages
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ADE7759
Channel 1 ADC Gain Adjust
The ADC gain in Channel 1 can be adjusted by using the multiplier
and Active Power Gain register (APGAIN[11:0]). The gain of the
ADC is adjusted by writing a two’s complement 12-bit word to
the Active Power Gain register. Below is the expression that
shows how the gain adjustment is related to the contents of the
Active Power Gain register.
Code
=
ADC
×
1 +
APGAIN
212
For example, when 7FFh is written to the Active Power Gain
register the ADC output is scaled up by 50%. 7FFh = 2047
decimal, 2047/212 = 0.5. Similarly, 801h = 2047 decimal
(signed two’s complement) and ADC output is scaled by –50%.
These two examples are graphically illustrated in Figure 23.
Channel 1 Sampling
The waveform samples may also be routed to the WAVEFORM
register (MODE[14:13] = 1, 0) to be read by the system master
(MCU). In waveform sampling mode the WSMP bit (Bit 3) in
the Interrupt Enable register must also be set to Logic 1. The
Active Power and Energy calculation will remain uninterrupted
during waveform sampling.
When in waveform sample mode, one of four output sample
rates may be chosen by using bits 11 and 12 of the Mode regis-
ter (WAVSEL1, 0). The output sample rate may be 27.9 kSPS,
14 kSPS, 7 kSPS, or 3.5 kSPS—see Mode Register section. The
interrupt request output IRQ signals a new sample availability
by going active low. The timing is shown in Figure 24. The 20-bit
waveform samples are transferred from the ADE7759 one byte
(eight-bits) at a time, with the most significant byte shifted out first.
The 20-bit data word is right justified and sign extended to 24
bits (three bytes)—see Serial Interface section.
SAMPLING RATE (27.9kSPS, 14kSPS, 7kSPS, OR 3.5kSPS)
IRQ
SCLK
DIN
16s
READ FROM WAVEFORM
0 0 0 01 HEX
DOUT
SIGN
CHANNEL 1 DATA
– 20 BITS
Figure 24. Waveform Sampling Channel 1
CHANNEL 1 AND CHANNEL 2 WAVEFORM SAMPLING
MODE
In Channel 1 and Channel 2 waveform sampling mode
(MODE[14:13] = 01), the output is a 40-bit waveform sample
data that contains both the waveform samples from Channel 1
and Channel 2 ADCs. Figure 25 shows the format of the 40-bit
waveform output.
1 BYTE
BIT 39
CH2[19:16] CH1[19:16]
2 BYTES
CH1[15:0]
2 BYTES
BIT 0
CH2[15:0]
Figure 25. 40-Bit Combined Channel 1 and Channel 2
Waveform Sample Data Format
V1P
V1
2.42V, 1.21V, 0.6V
؋1, ؋2, ؋4,
؋8, ؋16
REFERENCE
{GAIN[4:3]}
{GAIN[2:0]}
MULTIPLIER DIGITAL LPF
PGA1
ADC 1
Sinc3
DIGITAL
INTEGRATOR*
∫
HPF
TO WAVEFORM
SAMPLE REGISTER
TO MULTIPLIER
V1N
801HEX–7FFHEX
50Hz
CHANNEL 1 (ACTIVE POWER)
DATA RANGE AFTER
INTEGRATOR (50Hz)
V1
0.5V, 0.25V,
0.125V, 62.5mV,
31.3mV, 15.6mV,
0V
ANALOG
INPUT
RANGE
APGAIN[11:0]
40000h
2851Fh
00000h
D7AE1h
C0000h
+FS
+63% FS
– 63% FS
– FS
ADC OUTPUT
WORD RANGE
CHANNEL 1 (ACTIVE POWER)
DATA RANGE
3C7AEh
+94.5% FS
2851Fh
+63% FS
1428Fh
00000h
+31.5% FS
EBD71h
– 31.5% FS
D7AE1h
– 63% FS
C3852h
– 94.5% FS
000h 7FFh 801h
APGAIN[11:0]
*WHEN DIGITAL INTEGRATOR IS ENABLED, FULL-SCALE OUTPUT DATA VARIES DEPENDING
ON THE SIGNAL FREQUENCY BECAUSE OF –20dB/DECADE FREQUENCY RESPONSE.
2E72Eh
1EF74h
F7BAh
00000h
F0846h
E108Ch
D18D2h
000h
7FFh
801h
60Hz
APGAIN[11:0]
+94.5% FS
+63% FS
+31.5% FS
– 31.5% FS
– 63% FS
– 94.5% FS
CHANNEL 1 (ACTIVE POWER)
DATA RANGE AFTER
INTEGRATOR (60Hz)
26B50h
+94.5% FS
19CE0h
0CE70h
+63% FS
+31.5% FS
00000h
F3190h
E6320h
– 31.5% FS
– 63% FS
D94B0h
000h 7FFh 801h
– 94.5% FS
APGAIN[11:0]
Figure 23. ADC and Signal Processing in Channel 1
–18–
REV. 0
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