SA9105E
The formula for calculating the Output Frequency (f) is given below:
FOSC
(I
I1
I
V1
) + (I
I2
I
V2
) + (I
I3
I
V3
)
f = 11.16 * FOUTX *
*
3.58MHz
3 * I
R 2
Where FOUTX = Nominal rated frequency (4Hz, 290Hz or 1160Hz)
FOSC
I
I1
, I
I2
, I
I3
I
R
= Oscillator frequency (2MHz ...... 4MHz)
= Input currents for current inputs (16µA at rated)
= Reference current (typically 50µA)
I
V1
, I
V2
, I
V3
= Input currents for voltage inputs (14µA at rated)
XTAL is a colour burst TV crystal (f = 3.5795 MHz) for the oscillator. The oscillator
frequency is divided down to 1.7897 MHz on-chip, to supply the digital circuitry and the
A/D converters.
Figure 1: Application Circuit for Three Phase Power/Energy Measurement.
MAINS VOLTAGES
LINE 1
LINE 2
LINE 3
N
R1
R2
R3
R1A
R2A
R3A
C4
0V
C5
1
2
3
40
39
38
5V
C9
R7
FROM CTs
R18
C6
R8
R9
R19
4
5
6
7
37
36
35
C10
VI1P
VI1N
VI2P
VI2N
VI3P
VI3N
2.5V
2.5V
C7
R20
R10
R11
R12
R13
SA9105A
DIP-40
IC-1
R15
34
+ C1
+ C2
+ C3
R6
R5
R4
R21
C14
R16
33
32
31
8
9
10
11
12
13
2.5V
R17
C11
30
29
28
27
26
25
24
23
22
21
5V
C13
P6
P5
C8
14
15
16
17
0V
FOUT3
FOUT2
FOUT1
0V
0V
0V
0V
18
19
20
XTAL
DR-00233
C12
R14
P14
0V
44/12
sames
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