CS5464 View Datasheet(PDF) - Cirrus Logic
Part Name
Description
MFG CO.
CS5464 Datasheet PDF : 46 Pages
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CS5464
V (V2)
I (I2)
Poff (P2off)
P (P2)
+
+Σ
Q (Q2)
ΣN
X
ΣN
X
PulseRateE
Vacoff
(V2acoff)
+
÷N
√
+Σ
VRMS
(V2RMS)
S (S2)
÷N
Iacoff
+
(I2acoff) X
X
Σ√
+
-
+
√
Σ
IRMS
(I2RMS)
Inverse
X
PF
(PF2)
QTRIG
(Q2TRIG)
X
ΣN
÷N
ΣN
÷N
PACTIVE
(P2ACTIVE)
QAVG
(Q2AVG)
E1
Energy-to-pulse
E2
E3
X
REGISTER NAMES (CHANNEL 2 REGISTER
NAMES) INDICATED IN SHADED AREAS.
Figure 5. Power Calculation Flow
from the calculated VRMS and IRMS as well as the appar-
ent power.
When the optional HPF in either channel is disabled, an
all-pass filter (APF) in the complement channel is imple-
mented. The APF has an amplitude response that is flat
within the channel bandwidth and is used for matching
phase in systems where only one channel’s HPF is en-
gaged. For more information, see 5.3 High-pass Filters
on page 17.
4.2 Voltage and Current Measurements
The digital filter output word is subject to a DC offset ad-
justment and a gain calibration (See Section 7. System
Calibration on page 39). The calibrated measurement is
available by reading the instantaneous voltage and cur-
rent registers.
The Root Mean Square (RMS in Figure 5) calculations
are performed on N instantaneous voltage and current
samples, Vn and In, respectively (where N is the cycle
count), using the formula:
4.3 Power Measurements
The instantaneous voltage and current samples are
multiplied to obtain the instantaneous power (see Fig-
ure 3 and 4). The product is then averaged over N con-
versions to compute active power and is used to drive
energy pulse output E1. Energy output E2 is config-
urable and can provide an energy sign, a pulse output
that is proportional to the apparent power, or a tamper
indicator. Energy output E3 provides a pulse output that
is proportional to the reactive power or the apparent
power. Output E3 can also be set to indicate the
PFMON comparator output or to indicate the sign of the
voltage applied to the voltage channel.
The apparent power (S, S2) is the combination of the
active power and reactive power, without reference to
an impedance phase angle, and is calculated by the
CS5464 using the following formula:
S = VRMS × IRMS
IRMS =
N–1
∑ In
n=0
--------------------
N
and likewise for VRMS, using Vn. IRMS and VRMS are ac-
cessible by register reads, which are updated once ev-
ery cycle count (referred to as a computational cycle).
Power Factor (PF, PF2) is the active power (PActive,
P2Active) divided by the apparent power (S, S2)
PF
=
-P----A---c---t--i-v---e-
S
The sign of the power factor is determined by the active
power.
The CS5464 calculates the reactive power (QTrig,
Q2Trig) utilizing trigonometric identities, using the formu-
la
QTrig = S2 – PA2 ctive
DS682PP1
15
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