SA9102F/SA9102H
The formula for calculating the output frequency (f) is given below:
FOSC
II .IV
f = 11.16
FOUTX
*
*
*
2
3.58MHz
IR
Where FOUTX = Nominal rated frequency (64Hz)
FOSC
= Oscillator frequency (2MHz ...... 4MHz)
II
= Input currents for current inputs (16µA at rated)
= Input currents for voltage inputs (14µA at rated)
= Reference current (typically 50µA)
IV
IR
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:
C1 and C2 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%.
C3 and C4 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.
R2, R1 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.
R1 = R2 = (IL/16µA) * RSH/2
Where IL
RSH
=
=
Line current
Shunt resistor/termination resistor
7/14
sames
SAMES [ SAMES ]
