SA2007H
FUNCTIONAL DESCRIPTION
The SA2007H is a CMOS mixed signal analog/digital
integrated circuit, which performs power/energy calculations
across a power range of 1000:1, to an overall accuracy of
better than Class 1.
The integrated circuit includes all the required functions for 1-
phase power and energy measurement such as oversampling
A/D converters for the voltage and current sense inputs, power
calculation and energy integration. Internal offsets are
eliminated through the use of cancellation procedures.
Referring to the block diagram (figure 1) the SA2007H has two
current sense channels and a voltage sense channel. The
voltage measured is multiplied with the current measured on
the two channels. The multiplied signals from each current
channel is fed to separate power to pulse rate blocks.
The power to pulse rate blocks generate pulses at a frequency
proportional to the instantaneous active power measured.
Pulses on output P1 represent energy measured on current
channel 1. The pulses on output P2 represent energy
measured on current channel 2. Counting the pulses
generated represents the energy measured.
A typical application would be to simultaneous measure
energy/power consumption in both Live and Neutral lines. A
meter tamper condition could be detected when an imbalance
exists between the live and neutral energy/power measured.
Two modes of operation is available on the SA2007H, in one
mode the device is functionally the same as two SA2002H
devices sharing a common voltage channel. Alternatively the
pulse output is latched and an interrupt is generated on any
change of the pulse outputs.
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POWER CALCULATION
In Figure 8, the voltage drops across the current transformers
terminating resistors are converted to currents for each
current sense input, by means of resistors R
10
and R
11
(channel
1) as well as R
12
and R
13.
(channel 2). The current sense input
saturates at an input current of ±25µA peak.
The mains voltage (230VAC) is divided down through a divider
to 14V
RMS
. The current into the A/D converter input is set at
14µA
RMS
at nominal mains voltage, via resistor R
7
(1MW).
In this configuration, with a mains voltage of 230V and a
current of 80A, the output frequency measured on P1 or P2 pin
is 1360Hz. In this case the energy associated with a single
pulse is 18.4kW/1360Hz = 13.5Ws per pulse.
ANALOG INPUT CONFIGURATION
The input circuitry of the current and voltage sensor inputs are
illustrated in figure 3. These inputs are protected against
electrostatic discharge through clamping diodes.
The feedback loops from the outputs of the amplifiers A
I
and A
V
generate virtual shorts on the signal inputs. Exact duplications
of the input currents are generated for the analog signal
processing circuitry.
ELECTROSTATIC DISCHARGE (ESD)
PROTECTION
The SA2007H integrated circuit's input's/outputs are protected
against ESD.
POWER CONSUMPTION
The power consumption rating of the SA2007H integrated
circuit is less than 30mW.
V DD
IIP
CURRENT
SENSOR
INPUTS
VSS
VDD
A
I
IIN
VSS
VDD
IVP
VOLTAGE
SENSOR
INPUT
V SS
A
V
GND
DR-01288
Figure 3: Analog input internal configuration
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PRELIMINARY
SAMES [ SAMES ]
