SA2007P
FUNCTIONAL DESCRIPTION
The SA2007P 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
single 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. The SA2007P incorporates an anti-tamper
scheme by continuously measuring the power consumption on
both LIVE and NEUTRAL lines. A fault is indicated when these
measurements differ by more than 12.5%. The SA2007P
generates pulses with a frequency proportional to the larger of
the two current measurements. The source (LIVE or
NEUTRAL) for these pulses is indicated on the SEL1 pin. The
metering of energy consumption is taken from the source,
which shows the higher consumption.
Various pulse outputs (MOP MON and LED) are available.
,
The pulse rate on these pins follows the active power
consumption measured.
A low voltage stepper may be driven directly from the device by
connecting it between the MOP and MON pins, alternatively an
impulse counter may be driven directly by connecting it
between MOP and V
SS
.
The SA2007P configures itself from an external low cost
EEPROM that contain all meter configurations and calibration
data. No external trimming is required for this device.
Calibration of the meter may be fully automated.
POWER CALCULATION
In Figure 7, 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).
See Device Configuration for more details on the processing of
measured energy to frequency outputs.
GND
DR-01288
sames
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.
AUTOMATIC DEVICE CONFIGURATION (BOOT UP)
During power up, registers containing configuration and
calibration information are updated from an external
EEPROM. The device itself never writes to the EEPROM so
any write protect features offered by manufacturer of
EEPROM's may be used to protect the configuration and
calibration data of the meter. The device reloads its
configuration every 1193 seconds from the external EEPROM
in order to ensure correct operation of the meter. Every data
byte stored in the EEPROM is protected with a checksum byte
to ensure data integrity.
ELECTROSTATIC DISCHARGE (ESD)
PROTECTION
The SA2007P integrated circuit's input's/outputs are protected
against ESD.
POWER CONSUMPTION
The power consumption rating of the SA2007P 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
Figure 3: Analog input internal configuration
4/12
PRELIMINARY
SAMES [ SAMES ]
