STPM01 datasheet(44/60 Pages) STMICROELECTRONICS

44 / 60 page

Theory of operation

STPM01

44/60

Doc ID 10853 Rev 8

activate SYN first in order to latch the results;

after at least 1µs activate SCS;

write one byte to the transmitter of SPI (this will produce 8 pulses on SCL with SDI=1);

deactivate SYN;

optionally read the data records (the sequence of reading will be altered;

deactivate SCS;

Permanent writing of the CFG bits

In order to make a permanent set of some CFG bits, the following procedure should be

conducted:

collect all addresses of CFG bits to be permanently set into some list;

clear all OTP shadow latches;

set the system signal RD;

connect a current source of at least +14 V, 1 mA to 3 mA to VOTP;

wait for VOTP voltage is stable;

set one OTP shadow latch from the list;

set the system signal WE;

wait for 300 µs;

clear the system signal WE;

10. clear the OTP shadow latch which was set in step 6;

11. until all wanted CFG bits are permanently set, repeat steps 5 to 11;

12. disconnect the current source;

13. wait for VOTP voltage is less than 3 V;

14. clear the system signal RD;

15. read all data records, in the last two of them there is read back of CFG bits;

16. if verification of CFG bits fails and there is still chance to pass, repeat steps 1 to 16.

For steps of set or clear apply the timing shown in Figure 27 with proper signal on the

SDATD. For step 15 apply the timing shown in Figure 26.

For permanent set of the TSTD bit, which will cause no more writing to the Configuration

bits, the procedure above must be conducted in such way that steps 6 to 13 are performed

in series during single period of active SCS because the idle state of SCS would make the

signal TSTD immediately effective which in turn, would abort the procedure and possibly

destroy the device due to clearing of system signal RD and so, connecting all gates of 3V

NMOS sense amplifiers of already permanently set CFG bits to the VOTP source.

8.24

Energy calculation algorithm

Inside the STPM01 the computing section of the measured active power uses a completely

new signal patented process approach. This approach allows the device to reach high

performances in terms of accuracy.

The signals, coming from the sensors, for the instantaneous voltage:

Equation 2

v(t) = V•sin

ωt; where V is the peak voltage and ω is related to the line frequency

and the instantaneous current:

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