SA9102F/SA9102H
The formula for calculating the output frequency (f) is given below:
f = 11.16 * FOUTX *
Where FOUTX
FOSC
I
I
I
V
I
R
FOSC
3.58MHz
*
I
I
.I
V
I
R 2
= Nominal rated frequency (64Hz)
= Oscillator frequency (2MHz ...... 4MHz)
= Input currents for current inputs (16µA at rated)
= Input currents for voltage inputs (14µA at rated)
= Reference current (typically 50µA)
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.
TYPICAL APPLICATIONS
In the Application Circuits (Figures 1 and 2), the components required for power metering
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 SA9102F and SA9102H integrated
circuits 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 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 SA9102F/SA9102H
at maximum line current.
Values for RSH of less than 200µΩ should be avoided.
R
1
= R
2
= (I
L
/16µA) * R
SH
/2
Where I
L
= Line current
RSH
= Shunt resistor/termination resistor
sames
7/14
SAMES [ SAMES ]
