SA2007M
FUNCTIONAL DESCRIPTION
The SA2007M 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. The
SA2007M 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 SA2007M
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.
Frequency outputs (MOP, MON and LED) are available. The
pulse rate on these pins follows the instantaneous 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
.
POWER CALCULATION
In Figure 6, 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).
Different pulse rates are available at the MOP and MON pins.
The device may be programmed for a 1 pulse/kWh, 10
pulses/kWh or 100 pulses/kWh output, depending on the
status of the motor pulse rate select pins MP0 and MP1.
The LED pulse rate is fixed at 6400 pulses per kWh. Rated
conditions such as 230V/20A, 230V/40A and 230V/60A may
be chosen with the rated pin. This facility allows meter
manufacturers to cater for a wide range of metering
applications with minimal design changes.
IVP
VOLTAGE
SENSOR
INPUT
sames
ANALOG INPUT CONFIGURATION
The input circuitry of the current and voltage sensor inputs are
illustrated below.
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 SA2007M integrated circuit's input's/outputs are protected
against ESD.
POWER CONSUMPTION
The power consumption rating of the SA2007M integrated
circuit is less than 30mW.
V DD
IIP
CURRENT
SENSOR
INPUTS
VSS
VDD
A
I
IIN
VSS
VDD
V SS
A
V
GND
DR-01288
Figure 3: Analog input internal configuration
4/10
PRELIMINARY
SAMES [ SAMES ]
