STPM14 STMicroelectronics, STPM14 Datasheet - Page 23

• Manufacturer Part Number: STPM14
• Description: (STPM11 - STPM14) Single phase energy metering IC
• Manufacturer: STMicroelectronics

STPM11/12/13/14
Table 12.
7.14
Table 13.
LVS (1 Bit)
KMOT (2 Bits)
0
0
0
0
1
1
1
1
Different settings for led signal
Due to the innovative and proprietary power calculation algorithm, the frequency signal is
not affected by any ripple at twice the line frequency. This feature strongly reduces the
calibration time of the meter.
Driving a stepper motor
The STPM1X is able to directly drive a stepper motor. An internal divider (mono-flop and
decoder) generates stepper driving signals MA and MB from signal AW. The MA and MB
signals are brought to the MOP and MON pins that are able to drive the stepper motor.
Several kinds of selections are possible for the driving signals according to the configuration
bits LVS and KMOT.
The numbers of pulses per kWh (PM) in the MOP and MON outputs are linked with the
number of pulses of the LED P (see previous paragraph - 7.13) pin with the following
relationship.
Configuration of Mop and Mon Pins
The mono-flop limits the length of the pulses according to the LVS bit value.
The decoder distributes the pulses to MA and MB alternatively, which means that each of
them has only one half of selected frequency.
In case of detected negative power the behavior of MOP and MON depends on the ABS
configuration bit status. If this bit is set, the negative power is computed as it was positive
(absolute value), and the MOP and MON signals maintain the pulse sequence in order to
keep the forward rotation direction of the motor. If ABS is zero, negative power is computed
with its own sign, and the MOP and MON signals invert their logic state in order to make the
backward rotation direction of the motor. See the diagram below.
0
1
2
3
KMOT (2 Bits)
0
1
2
3
0
1
2
3
Pulses
APL=0
P
Pulses length
156.25 ms
156.25 ms
156.25 ms
156.25 ms
31.25 ms
31.25 ms
31.25 ms
31.25 ms
Theory of operation
Pulses
APL=1
P/128
P/256
P/64
P/32
P/1280
P/2560
P/128
P/256
P/640
P/320
P/64
P/32
PM
23/43