PM9103AP
Reset Integrator:
status.
The integrator is reset without transmitting the integrator
Read/Reset Integrator:
The device transmits the integrator status and resets the
integrator after the current measurement cycle has been completed.
In a typical application, the system controller monitors the status of the on-chip
integrator using the "Read" command.
If after a "Read" command, the integrator value is sufficiently high, a "Read/Reset"
command from the controller causes the integrated circuit to complete the existing
measurement cycle, transmit the 16 most significant bits of the 22 bit integrator
via the Serial Output, to the controller and restart the integrator.
The most significant bit of the 16 bits, indicates the direction of energy consumption
measured (0 = Positive, 1 = Negative).
Refer to the SA9103C, SA9103E or SA9603C datasheets for the serial interface
command protocols.
6.
Circuit Description
The Application Circuit (figure 2) shows the components required for the serial
interface power metering module, using a shunt resistor for current sensing.
In this application the device requires +2.5V, 0V, -2.5V DC supply.
The most important external components are:
C
1
and C
2
are the outer loop capacitors of the two integrated oversampling A/D
converters. The value of these capacitors is 560pF. The actual values determine
signal to noise and stability performance. The tolerance should be within ±10%.
C
3
and C
4
are the inner loop capacitors of the A/D converters. The optimum value
is 3.3nF. The actual values are uncritical. Values smaller than 0.5nF and larger
than 5nF should be avoided.
R
2
, R
1
and RSH are the resistors defining the current level into the current sense
input. The values should be selected for an input current of 16µA
RMS
into the SA9103
/ SA9603C at maximum line current.
Values for RSH of less than 200µΩ should be avoided.
R
1
= R
2
= I
L
/16µA
RMS
* R
SH
/2.
Where
I
L
= Line current
= Shunt resistor/terminating resistor
RSH
R
3
, R
6
and R
4
set the current for the voltage sense input. The values should be
selected so that the input current into the voltage sense input (virtual ground) is set
to 14µA
RMS
.
R
7
defines all on-chip bias and reference currents. With R
7
= 24kΩ, optimum
conditions are set.
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SAMES [ SAMES ]
