ADE7569ASTZF16 Analog Devices Inc, ADE7569ASTZF16 Datasheet - Page 50

• Manufacturer Part Number: ADE7569ASTZF16
• Description: IC ENERGY METER MCU 16K 64LQFP
• Manufacturer: Analog Devices Inc

Specifications of ADE7569ASTZF16

• Applications: Energy Measurement
• Core Processor: 8052
• Program Memory Type: FLASH (16 kB)
• Controller Series: ADE75xx
• Ram Size: 512 x 8
• Interface: I²C, SPI, UART
• Number Of I /o: 20
• Voltage - Supply: 3.135 V ~ 3.465 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 64-LQFP
• Ic Function: Single Phase Energy Measurement IC
• Supply Voltage Range: 3.13V To 3.46V, 2.4V To 3.7V
• Operating Temperature Range: -40°C To +85°C
• Digital Ic Case Style: LQFP
• No. Of Pins: 64
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

ADE7116/ADE7156/ADE7166/ADE7169/ADE7566/ADE7569
ANALOG-TO-DIGITAL CONVERSION
Each ADE7116/ADE7156/ADE7166/ADE7169/ADE7566/
ADE7569 has two Σ-Δ analog-to-digital converters (ADCs). The
outputs of these ADCs are mapped directly to waveform sampling
SFRs (Address 0xE2 to Address 0xE7) and are used for energy
measurement internal digital signal processing. In PSM1 (battery
mode) and PSM2 (sleep mode), the ADCs are powered down to
minimize power consumption.
For simplicity, the block diagram in Figure 44 shows a first-
order Σ-Δ ADC. The converter is made up of the Σ-Δ modulator
and the digital low-pass filter (LPF).
A Σ-Δ modulator converts the input signal into a continuous
serial stream of 1s and 0s at a rate determined by the sampling
clock. In the ADE7116/ADE7156/ADE7166/ADE7169/ADE7566/
ADE7569, the sampling clock is equal to 4.096 MHz/5. The
1-bit DAC in the feedback loop is driven by the serial data
stream. The DAC output is subtracted from the input signal. If
the loop gain is high enough, the average value of the DAC
output (and, therefore, the bit stream) can approach that of the
input signal level.
For any given input value in a single sampling interval, the data
from the 1-bit ADC is virtually meaningless. Only when a large
number of samples are averaged is a meaningful result obtained.
This averaging is carried into the second part of the ADC, the
digital LPF. By averaging a large number of bits from the
modulator, the low-pass filter can produce 24-bit data-words
that are proportional to the input signal level.
The Σ-Δ converter uses two techniques to achieve high
resolution from what is essentially a 1-bit conversion technique.
The first is oversampling. Oversampling means that the signal is
sampled at a rate (frequency) that is many times higher than the
bandwidth of interest. For example, the sampling rate in the
LOW-PASS FILTER
ANALOG
R
C
+
–
Figure 44. First-Order
INTEGRATOR
Rev. B | Page 50 of 152
V
REF
1-BIT DAC
MCLK/5
ADE7116/ADE7156/ADE7166/ADE7169/ADE7566/ADE7569
is 4.096 MHz/5 (819.2 kHz), and the band of interest is 40 Hz to
2 kHz. Oversampling has the effect of spreading the quantization
noise (noise due to sampling) over a wider bandwidth. With the
noise spread more thinly over a wider bandwidth, the quantiza-
tion noise in the band of interest is lowered (see Figure 43).
However, oversampling alone is not efficient enough to improve
the signal-to-noise ratio (SNR) in the band of interest. For example,
an oversampling ratio of four is required to increase the SNR by
only 6 dB (1 bit). To keep the oversampling ratio at a reasonable
level, it is possible to shape the quantization noise so that the
majority of the noise lies at the higher frequencies. In the Σ-Δ
modulator, the noise is shaped by the integrator, which has a
high-pass-type response for the quantization noise. The result is
that most of the noise is at the higher frequencies where it can
be removed by the digital LPF. This noise shaping is shown in
Figure 43.
SIGNAL
SIGNAL
... 10100101 ...
Σ
-∆ ADC
COMPARATOR
NOISE
NOISE
LATCHED
0
0
Figure 43. Noise Reduction Due to Oversampling and
OUTPUT FROM DIGITAL
2
2
Noise Shaping in the Analog Modulator
HIGH RESOLUTION
DIGITAL
FILTER
LPF
LOW-PASS
DIGITAL
FILTER
FREQUENCY (kHz)
FREQUENCY (kHz)
FILTER (RC)
ANTIALIAS
409.6
409.6
24
SHAPED
NOISE
FREQUENCY
SAMPLING
819.2
819.2