STPM14 STMicroelectronics, STPM14 Datasheet - Page 17

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

STPM11/12/13/14
Table 10.
7.6
VI
Nominal voltage values
For example, if R1 = 783kΩ and R2 = 475Ω are used as resistor divider when the line
voltage is present, the positive voltage present at the input of the voltage channel of
STPM1x is:
since the maximum voltage value applicable to the voltage channel input of STPM1x is
+0.3V, the equivalent maximum line voltage applicable is:
V
considering the case of NOM=2, the correspondent RMS values used for energy
computation is:
V
Usually the supply voltage for the electronic meter is taken from the line voltage. In SWM,
since the line voltage is no longer present, another power source must be used in order to
provide the necessary supply to STPM1x and the other electronic components of the meter.
Power supply
The main STPM1X supply pin is the V
the necessary voltage for the analog part V
V
should be connected between V
capacitors must be located very close to the device.
The STPM1X contains a Power-On-Reset (POR) detection circuit. If the V
than 2.5V, then the STPM1X goes into an inactive state, all the functions are blocked
asserting and a reset condition is set. This is useful to ensure that the correct device
operation at power-up and during power-down. The power supply monitor has built-in
hysteresis and filtering, which give a high degree of immunity to false triggering due to noisy
supply voltages.
A BandGap voltage reference (VBG) of 1.23V ±1% is used as reference voltage level source
for the two linear regulators and for the A/D converters. Also, this module produces several
bias currents and voltages for all other analog modules and for the OTP module. The
bandgap voltage temperature behavior can be changed in order to better compensate the
variation of sensor sensitivity with temperature. This task is performed with the BGTC
configuration bits.
PK
RMS
SS
=
= R
pin represents the reference point for all the internal signals. The 100nF capacitor
R
= V
1
1
R
+
+R
PK
2
NOM
R
2
0
1
2
3
2
• 0.4219 = 208.76 [V]
/R
⋅
V
2
RMS
• 0.3 = 494.82
2
CC
and V
CC
pin. From the V
SS
DDA
, V
DDA
(3V) and for the digital part V
and V
CC
SS
pin two linear regulators provide
, V
0.3594
0.3906
0.4219
0.4531
DDD
K
NOM
and V
Theory of operation
SS
CC
. All these
DDD
supply is less
(1.5V). The
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