SA9605A
FUNCTIONAL DESCRIPTION
The SA9605A is a CMOS mixed signal integrated circuit,
which performs three phase power/energy calculations over
a range of 500:1, to an overall accuracy of Class 1.
A/D converters are 14μARMS through the resistors R5 (1M
each). The trimpots P1 are used for calibration purposes. The
capacitors C1 are used to compensate the phase shift of the
current transformers.
The SA9605A is functionally similar to the SA9105E and
SA9105F with the advantage of no external loop capacitors.
For the current sense inputs the voltage drop across the
current transformer’s terminating resistors RT are converted
to currents of 16μARMS for rated conditions, by means of
resistors R1 and R2. The signals providing the current
information are applied to the paired current sensor inputs,
IIP1/IIN1, IIP2/IIN2 and IIP3/IIN3. The current sense inputs
saturate at an input current of ±25μA peak.
The integrated circuit includes all the required functions for
three 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 SA9605A generates pulses, the frequency
of which is proportional to the power consumption. Two
frequency outputs (FOUT1 and FOUT2) are available. The
pulse rate follows the instantaneous power measured.
In this configuration, with the mains voltage of 3 x 220 V and
rated currents of 80A, the output frequency of the SA9605A
energy metering integrated circuit at FOUT1 is 1160Hz. In
this case 1 pulse will correspond to an energy consumption
of 3 x 17.6kW/1160Hz = 45.5Ws.
POWER CALCULATION
In the application circuit (see Figure 3), the mains voltages
from L1, L2 and L3, are converted to currents and applied to
the voltage sense inputs IVP1, IVP2 and IVP3. The current
levels on the voltage sense inputs are derived from the mains
voltage (3 x 220 VAC) being divided down through voltage
dividers to 14V. The resulting input currents into the
The output frequency at FOUT1 and FOUT2 represents the
absolute sum of the energy measured on all three phases,
regardless of the direction of energy flow through the current
sensors. This measurement method will assist meter
manufacturers to circumvent meter tampering by reversal of
the phases.
VDD
N
GND
Power
Supply
L1
L2
L3
VSS
VDD
U1
IIN1
R1
VDD
OSC1
RT1
CT1
R3
OSC2
FOUT1
FOUT2
R2
IIP1
Pulse Output 1
R5
IVP1
Pulse Output 2
Direction Output
C1
DIR
N
R4
AGND
VREF
PGM0
L3
L2
L1
GND
PGM1
VSS
SA9605A
P1
Repeat for
Phases 2
and 3
R6
GND
VSS
Figure 3: Application Circuit
SPEC-3118 (REV. 3)
29-09-2017
4/11
SAMES [ SAMES ]
