STPMC1 ST Microelectronics, STPMC1 Datasheet - Page 24

• Manufacturer Part Number: STPMC1
• Description: Programmable poly-phase energy calculator IC
• Manufacturer: ST Microelectronics

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Theory of operation
Figure 9.
9.6
Table 12.
24/76
4.194 MHz
4.915 MHz
8.192 MHz
9.830 MHz
f
XTAL
ZCR signal
Period and line voltage measurement (status bits: LIN, BFR,
LOW, BFF)
From voltage channels, a base frequency signal LIN is obtained, which is high when the line
voltage is rising and it is low when the line voltage is falling, so that, LIN signal represents
the sign of dv/dt. With further elaboration, the ZCR signal is also produced.
A period meter, which is counting up pulses of f
period of voltage channel base frequency and checks if the voltage signal frequency is in the
band going from f
This is done, phase by phase, by means of the signal LIN, which trailing edge is extracted
and it is used to reset the period meter.
Good frequency ranges for different clock source values
If the counted number of f
2
base frequency exceeds the lower limit and an error flag BFR is set. This error flag is part of
the 8-bit status byte of each phase (see
If the counted number of f
2
must be repeated three times, in order to set the error flag BFR, as shown in
18
16
equivalent pulses or if the counting is never stopped (no more LIN trailing edge), the
equivalent pulses, the base frequency exceeds the upper limit. In this case, such error
8.389 MHz
9.830 MHz
8.192 MHz
9.830 MHz
f
MCLK
MCLK
/(2
18
MCLK
MCLK
- 2
3
/8 pulses between two trailing edges of LIN is higher than the
Doc ID 15728 Rev 1
/8 pulses between two trailing edges of LIN is lower than the
)
freq. min. = f
f
MCLK
32.0 Hz
37.5 Hz
31.3 Hz
37.5 Hz
Table
/2
18
MCLK
to f
30).
MCLK
MCLK
/2
18
/8 reference signal, measures the
/2
16
.
freq. max. = f
128.0 Hz
150.0 Hz
125.0 Hz
150.0 Hz
Figure
MCLK
/2
STPMC1
16
10.