STPM32 datasheet(56/121 Pages) STMICROELECTRONICS

Part #	STPM32

Description	ASSP for metering applications with up to four independent 24-bit 2nd order sigma-delta ADCs, 4 MHz OSF and 2 embedded PGLNA

PDF	121 Pages

Scroll/Zoom	100%

Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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56 / 121 page

Theory of operation

STPM32, STPM33, STPM34

56/121

DS10272 Rev 8

Figure 42. Sag and swell detection blocks

Voltage sag detection

To detect a voltage sag, the fundamental component of voltage is compared to the 10-bit

threshold SAG_THRx[9:0] in DSP_CR5 and DSP_CR7 for primary and secondary channel

respectively.

An internal time counter is incremented until momentary voltage value is below the

threshold. Sag event is recorded when the timer counter reaches a programmable value set

by SAG_TIME_THR[13:0] bits in DSP_CR3. This time threshold is unique for both

channels.

When a sag event is detected, LSB of SAGx_EV[3:0] event register and SAG_Start bit are

set in the interrupt status register and an interrupt is generated.

If sag event ceases, SAGx_EV register is left shifted and zero is added as LSB, besides,

SAG_end bit in the interrupt status register is set as well.

The duration of the event is stored in SAGx_TIME[14:0] in DSP_REG16 and DSP_REG18

for primary and secondary voltage channel respectively.

If the overflow of SAG_TIME register occurs, SAGx_EV register is left shifted and its LSB is

set, as shown in Figure 43.

LSB of time registers is 8

s.

To disable sag detection, the SAG_THRx register must be set to zero.

STPM32 Datasheet(PDF) 56 Page - STMicroelectronics