STPM01FTR datasheet(31/60 Pages) STMICROELECTRONICS

31 / 60 page

STPM01

Theory of operation

Doc ID 10853 Rev 8

31/60

It is expected that an application microcontroller should access the data in the metering

device on regular basis at least 1/s (recommended is 32/s). Every latching of results in the

metering device requested from the microcontroller also resets the watchdog. If latching

requests does not follow each other within 1.6 second, an active high pulse on MON is

produced, because device assumes that microcontroller does not operate properly. An

application can use this signal either to control the RESET pin of its microcontroller or it can

be tied to some interrupt pin. The last possibility is recommended for a battery backup

application which can enter some sleep mode due to power down condition and should not

be reset by metering device because it would exit from the sleep mode.

The LED pin can be driven from AW wide band (active energy as in standalone mode), AW

limited at fundamental, RW (reactive energy) or SW (apparent energy) according to the

value of KMOT bit.

In this case, since the LED pin is driven by signals different from AW, some other

relationship between the LSB of the register and must be defined:

KAWFund = 4*KAW [Wh]

KRW = 2*KAW [VARh]

KSW = KAW [VAh]

APL = 1:

MOP provides the

∑ Δ signal generated from the analog voltage input;

MON provides the

∑ Δ signal generated from the analog current input, according to the

selection of the tamper module

LED provides the information about the selection of the current channel made by the tamper

module. If LED is low it means the primary channel is selected, if LED is high the secondary

channel is actually selected.

8.17

Status bits

The STPM01 includes 8 status bits that provide several information on the current meter

status. The status bits are the following:

Table 14.

LED pin configuration in peripheral mode

KMOT (2 Bits)

Signal available in LED pin

# of Pulses

AW Type 0 (1)

P [kWh]

AW Type 1 (1)

P [kWh]

2RW

P [kVARh]

P [kVAh]

* Type0 is the Wide band Active Energy and Type1 is the fundamental Active Energy if FUND=0, if FUND=1 they are

swapped.

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