STPM34 datasheet(40/89 Pages) STMICROELECTRONICS

40 / 89 page

In the same way:

VSWELL: target RMS value of swell voltage

AV: voltage sensor gain

DSWELL= 210, length of swell threshold register

calV = 0.875, calibrator mid value

Following the above calculation we obtain the hexadecimal value of voltage swell threshold:

Table 16. Voltage swell

Parameter

Value

SWELLV=VSWELLVref∙AV∙ 2∙ R2R1+R2∙calV∙DSWELLHEX

LSBSWELL_V= Vref∙R1+R2

AV∙ 2∙R2∙calV∙DSWELL V

For the current swell, an analogue procedure can be followed:

ISWELL: target RMS value of swell current

kS: current sensor sensitivity [V/A]

AI: current sensor gain

calI= 0.875, calibrator mid value

The swell threshold is:

Table 17. Current swell

Parameter

Value

SWELLC=ISWELLVref∙AI∙ 2∙kS∙calI∙DSWELLHEX

LSBSWELL_C= Vref

AI∙ 2∙kS∙calI∙DSWELL A

8.4.11

Tamper detection

The device includes a tamper detection module (the STPM34 and STPM33 only).

To enable this feature, TMP_EN bit and TMP_TOL[1:0] tamper tolerance have to be set in DSP_CR3. Tamper

detection feature is disabled by default. It is possible to choose among four different tolerances according to

Table 18 :

Table 18. Tamper tolerance setting

TMP_TOL[1:0]

Tamper tolerance

0x00

TOL = 12.5%

0x01

TOL = 8.33%

0x10

TOL = 6.25%

0x11

TOL = 3.125%

Tamper module monitors active energy registers of the two channels. Tamper condition is detected when the

absolute value of the difference between the two active energy values is greater than the chosen percentage of

the averaged value. This occurs when the following equation is satisfied:

Equation 17

(17)

|EnergyCH1 - EnergyCH2| > TOL * |EnergyCH1 + EnergyCH2|

STPM32, STPM33, STPM34

Functional description of hardwired DSP

DS10272 - Rev 13

page 40/89

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