SA9106A
4.
Electrostatic Discharge (ESD) Protection
The SA9106A integrated circuit inputs/outputs are protected against ESD according
to Mil-Std 883C, method 3015.
Power Consumption
The power consumption rating of the SA9106A integrated circuit is less than 50mW,
excluding the display.
5.
TYPICAL APPLICATIONS
In the Application Circuits (Figures 1 and 2) the components required for power
measurement applications, are shown.
In Figure 1 a shunt resistor is used for current sensing. In this application, the circuitry
requires a +2.5V, 0V, -2.5V DC supply.
In the case of Figure 2, when using a current transformer for current sensing, a +5V, 0V
DC supply is sufficient.
The most important external components for the SA9106A integrated circuit are:
C
1
and C
2
are the outer loop capacitors for the two integrated oversampling A/D
converters. The value of these capacitors is 560pF.
The actual values determine the signal to noise and stability performance. The tolerances
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 into the SA9106A at maximum
line current.
Values for RSH of less than 200µΩ should be avoided.
R
1
= R
2
= (I
L
/16µA) * RSH/2
Where I
L
= Line current
RSH
= Shunt resistor/termination resistor
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.
R
7
together with the trimpot RT defines all on-chip bias and reference currents. The bias
resistor value (R
B
= R
7
+ RT) may be varied within ±10% for calibration purposes. Any
change to R
B
will affect the displayed value quadratically (i.e.: R
B
= +5%, Display value
= +10%).
XTAL is a colour burst TV crystal (f = 3.5795MHz) for the oscillator. The oscillator
frequency is divided down to 1.7897MHz on-chip to supply the digital circuitry and the
A/D converters.
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