Cirrus Logic CS5464 - Manual (Page 19)

CS5464
DS682F3 19
6. SETTING UP THE CS5464
6.1 Clock Divider
The internal clock to the CS5464 needs to operate
around 4 MHz. However, by using the internal clock di-
vider, a higher crystal frequency can be used. This is im-
portant when driving an external microcontroller
requiring a faster clock and using the CPUCLK output.
K is the divide ratio from the crystal input to the internal
clock and is selected with Configuration register (Con-
fig
) bits K[3:0]. It has a range of 1 to 16. A value of zero
results in a setting of 16.
6.2 CPU Clock Inversion
By default, CPUCLK is inverted from XIN. Setting Con-
figuration register bit iCPU removes this inversion. This
can be useful when one phase adds more noise to the
system than the other.
6.3 Interrupt Pin Behavior
The behavior of the INT pin is controlled by the IMODE
and IINV bits in the Configuration register as shown.
If IMODE = 1, the duration of the INT pulse will be two
DCLK cycles, where DCLK = MCLK/K.
6.4 Current Input Gain Ranges
Control register bits I1gain (I2gain) select the input
range of the current inputs.
6.5 High-pass Filters
Mode Control (Modes) register bits VHPF and IHPF ac-
tivate the HPF in the voltage and current paths, respec-
tively. Each energy channel has separate VHPF and
IHPF bits. When a high-pass filter is enabled in only one
path within a channel, a phase matching filter (PMF) is
applied to the other path within that channel. The PMF
filter matches the amplitude and phase response of the
HPF in the band of interest, but passes DC.
6.6 Cycle Count
Low-rate calculations, such as average power and RMS
voltage and current integrate over several (N) output
word rate (OWR) samples. The duration of this averag-
ing window is set by the Cycle Count (N) register. By de-
fault, Cycle Count is set to 4000 (1 second at output
word rate [OWR] of 4000 Hz). The minimum value for
Cycle Count is 10.
6.7 Energy Pulse Outputs
By default, E1 outputs active energy, E3, reactive ener-
gy, and E2, the sign of both active and reactive energy.
(See
Figure 2. Timing Diagram for E1, E2, and E3 on
page 13.)
Three pairs of bits in the Mode Control (Modes) register
control the operation of these outputs. These bits are
named E1MODE[1:0], E2MODE[1:0], and
E3MODE[1:0]. Some combinations of these bits over-
ride others, so read the following paragraphs carefully.
The E2 pin can output energy sign, apparent energy, or
energy channel in use (1 or 2). Table 4 lists the func-
tions of E2 as controlled by E2MODE[1:0] in the Modes
register.
Note: E2MODE[1:0]=3 is a special mode.
The E3 pin can output reactive energy, power fail mon-
itor status, voltage sign, or apparent energy. Table 5
IMODE IINV INT Pin
0 0 Active-low Level
0 1 Active-high Level
1 0 Low Pulse
1 1 High Pulse
Table 1. Interrupt Configuration
I1gain, I2gain Maximum Input Gain
0 ±250 mV 10x
1 ±50 mV 50x
Table 2. Current Input Gain Ranges
VHPF IHPF Filter Configuration
0 0 No filter on Voltage or Current
0 1 HPF on Current, PMF on Voltage
1 0 HPF on Voltage, PMF on Current
1 1 HPF on Current and Voltage
Table 3. High-pass Filter Configuration
E2MODE1 E2MODE0 E2 output
0 0 Energy Sign
0 1 Apparent Energy
1 0 Channel in Use
1 1 Enable E1MODE
Table 4. E2 Pin Configuration