SA4106A
Direction Select Input (DIRI)
When FMS is floating the LED pin outputs fast mode pulses.
The motor pulses occur as usual based on the last FMS
before a floating condition was detected as well as the current
states of R0, R1, R2 and R3. If a floating condition on FMS is
detected at device start-up the motor pulses are generated
Depending on the state of the DIRI pin the energy to be
measured can be positive energy only, negative energy only,
or both positive and negative energy. Connecting DIRI to VDD
will result in only positive energy being measured. Energy
flowing in the negative direction will not be measured.
Connecting DIRI to VSS will result in only negative energy
being measured. Energy flowing in the positive direction will
not be measured. Connecting the DIRI pin to the DIRO output
pin enables the bidirectional mode where energy is measured
regardless of direction.
based on FMS set to VSS
.
Rated Condition Select (R0, R1, R2, R3)
The Rated Condition Select inputs (R0, R1, R2 and R3) along
with the Fast Mode Select input (FMS) are used for obtaining
a multitude of meter constants and motor drive ratios. The
different LED and motor division factors (DF_LED and
DF_MO) that can be selected via R0, R1, R2, R3 and FMS
are shown Table 3.
Anti-Creep Threshold Select (ACSEL)
The Anti-Creep Threshold Select input (ACSEL) is used to
select between different anti-creep thresholds. The
thresholds that can be selected are shown in Table 2. The
anti-creep feature can also be disabled if required. In this
case an external microcontroller could be used to implement
any desirable anti-creep threshold.
To calculate the LED output pulse constant in STANDARD
mode and the motor drive pulse constant for any meter rating
(IMAX and VNOM) the following formulae can be used:
퐼푉푃
5000
1000 × 3600
퐿퐸퐷 ꢀ푚푝/푘푊ℎ =
×
×
16 퐷퐹_퐿퐸퐷 푉ꢉ푂푀 × 퐼푀퐴푋
Table 2: Anti-creep threshold selection via the ACSEL input
...(1)
ACSEL Input
VSS
Anti-Creep Threshold
Disabled
where
IMAX is maximum rated mains current,
VNOM is nominal mains voltage,
VDD
0.01% FMAX
Floating
0.004% FMAX
IVP is the analog input current on the voltage sense input at
VNOM as specified in Table 1 and
DF_LED is the dividing factor for the LED output that is set by
the combination of R0, R1, R2, R3 and FMS as specified in
Table 3.
The anti-creep threshold is defined as a percentage of the
maximum output frequency in FAST mode (FMAX). Any FAST
mode pulses that occur at a lower frequency are not passed
to the pulse dividers and pulse output circuits.
Equation 1 is based on the assumption that the input current
into the IIP/IIN current sense input is set to 16μARMS at IMAX
.
Fast Mode Select (FMS)
The Fast Mode Select input (FMS) is used to select between
STANDARD and FAST mode as well as to select between a
multitude of meter constants and motor drive dividing ratios.
Connecting this pin to VDD or VSS enables the STANDARD
mode of operation while leaving this pin floating enables the
FAST mode of operation. When STANDARD mode is
enabled the LED output pulses at a low frequency. This low
frequency allows a longer accumulation period and the output
pulse rate is therefore proportional to the average power
consumption measured.
퐿퐸퐷 ꢀ푚푝/푘푊ℎ
ꢇ표푡표푟 ꢀ푚푝/푘푊ℎ =
퐷퐹_ꢇꢊ
…(2)
where
LED imp/kWh is the LED constant as calculated using
Equation 1 and
DF_MO is the dividing factor for the motor output that is set
by the combination of R0, R1, R2, R3 and FMS as specified
in Table 3.
Table 4 illustrates some of the possible LED and motor
constants that are achievable for some common values of
IMAX using a VNOM between 220V and 240V.
The Rated Condition Select pins (R0, R1, R2, R3) together
with the FMS pin are used to select different LED output
frequencies which in turn determine the applications meter
constant. Refer to Figure 9 for the LED output timing diagram.
When the FAST mode is enabled the LED output generates
pulses at a nominal frequency of 5kHz at IMAX and VMAX. In
this mode the pulse frequency is proportional to the average
power consumption measured. This mode is useful when
interfacing to a microcontroller.
SPEC-1587 (REV. 5)
29-09-2017
10/18
SAMES [ SAMES ]
