STPMC1 ST Microelectronics, STPMC1 Datasheet - Page 27

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

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STPMC1
Table 13.
9.9
LTCH (2 bits)
The no-load condition occurs when the product between U
a given value. This value can be set by the LTCH configuration bits. Four different no-load
threshold values can be chosen according to the two LTCH bits as reported in
When a no-load condition occurs (BIL = 1) the integration of power is suspended. The no-
load condition flag BIL in standalone mode blocks generation of pulses for stepper and is
brought out to the output selector forcing SCLNLC pin low. In peripheral mode, the BIL
signal can be accessed through the SPI interface.
The minimum output frequency (at no-load threshold) is given as % of the full-scale (FS)
output frequency, where FS internal AW frequency is 1370 Hz per phase.
No-load detection thresholds
Example 3: No-load condition threshold calculation
In NLC function is also implemented an hysteresis. When the current is falling the threshold
is half lower than that described above.
Error detection (status bits: BCF, PIN)
The STPMC1 has two error detection circuits that checks:
●
●
The first error detection circuit checks if any of the
1 or 0 within the period of observation (250 µs). In case of detected error the corresponding
error occurs the correspondent phase bit BCF is set. When the
again the BCF flag is cleared immediately.
signal is replaced with an idle
An energy meter has a power constant of C = 64000 pulses/kWh on LED pin.
It is valid the following relation:
C = 3600000 * f / P
where 3600000 is the factor between kWh and Ws and f is the output frequency on the
LED pin if P power is applied to the meter.
The minimum output frequency if LTCH [0] = LTCH [1] = 1 is:
f = 0,010 * 1370 Hz = 0,137 Hz
which gives a no-load condition power threshold equal to:
P = 3600000 * 0,137 Hz / 64000imp/kWh = 7,7 W
In this example, the no-load threshold is equivalent to 7,7 W of load or to a start-up
current of 32 mA at 240 V.
the
the state of output pins
0
1
2
3
signals
Doc ID 15728 Rev 1
signal, which represents a constant value 0. When this
NLC threshold
0,00125*FS
signals from the analog part is stuck at
0,0025*FS
0,005*FS
0,010*FS
X
and I
X
signal becomes correct
register values is below
Theory of operation
Table
13.
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