STPM01 datasheet(24/60 Pages) STMICROELECTRONICS

24 / 60 page

Theory of operation

STPM01

24/60

Doc ID 10853 Rev 8

When a no load condition occurs (BIL=1) the integration of power is suspended and the

tamper module is disabled.

In standalone mode, if a no load condition is detected, the BIL signal blocks generation of

pulses for stepper and forces SCLNLC pin to be low. If APL = 2 (see Section 8.14) the LED

pin continues providing the high frequency pulses, while if APL = 3, the pulses are stopped

as happens for MOP and MON.

In peripheral mode, the BIL signal can be accessed only through the SPI interface.

8.9

Error detection

In addition to the no load condition and the line frequency band, the integration of power can

be suspended also due to detected error on the source signals.

There are two kinds of error detection circuits involved. The first checks all the

∑ Δ signals

from the analog part if any is stacked at 1 or 0 within the 1/128 of fCLK period of observation.

In case of detected error the corresponding

∑ Δ signal is replaced with an idle ∑ Δ signal,

which represents a constant value 0. All error and other resolved flags are treated as bits of

a device status and can be read out by means of SPI interface.

Another error condition occurs if the MOP, MON and LED pin outputs signals are different

from the internal signals that drive them. This can occur if some of this pin is forced to GND

or to some other imposed voltage value. In this case the internal status bit PIN is activated

providing the information that some hardware problem has been detected, for example the

stepper motor has been mechanically blocked.

8.10

Tamper detection module

The STPM01 is able to measure the current in both live and neutral wire with a time domain

multiplexing approach on a unique sigma delta modulator. This mechanism is adopted to

implement anti-tamper function. If this function is selected (see Table 9), the live and neutral

wire currents are monitored; when the difference between the two measurements exceeds a

rated threshold the STPM01 enters the "tamper state", while in "normal state" the two

measurements are below the threshold.

In particular, both channels are not observed all the time, rather a time multiplex mechanism

is used. During the observation time of each channel, its active energy is calculated. A

tamper condition occurs when the absolute value of the difference between the two active

energy values is greater than a certain percentage of the averaged energy during the

activated tamper module (see Equation 1: ).

This percentage value can be selected between two different values (12.5 % and 6.25 %)

according to the value of the configuration bit CRIT.

The tamper condition is detected when the following formula is satisfied:

Equation 1

EnergyCH1 - EnergyCH2 > KCRIT (EnergyCH1 + EnergyCH2)/2;

where KCRIT can be 12.5 % or 6.25 %.

The detection threshold is much higher than the accuracy difference of the current channels,

which should be less than 0.2 %, but, some headroom should be left for possible transition

effect, due to accidental synchronism of actual load current change with the rhythm of taking

the energy samples.

STPM01 数据表(PDF) 24 Page - STMicroelectronics

STPM01 数据表(HTML) 24 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

数据表下载