Cirrus Logic CS5462 - Manual (Page 10)

CS5462
10 DS547F1
4. FUNCTIONAL DESCRIPTION
4.1 Programmable Gain Amplifier (PGA)
The CS5462 is equipped with a PGA on the current
channel. While the voltage channel is always set to
a 10x differential input voltage range (500 mV
P-P
),
the current channel can be set to one of two differ-
ent input ranges. The maximum differential voltage
range on the current channel can be set to 10x
(500 mV
P-P
) and 50x (100 mV
P-P
).
The gain setting of the current channel’s PGA and
also the high pass filter option are selected by con-
necting the IGAIN pin to one of seven Program Se-
lect output pins. For all applications the IGAIN pin
must be tied to one and only one Program Select
pins. Figure 2 below shows the different options
that can be selected at startup. These seven differ-
ent options allow the CS5462’s PGA to be set up in
either 10x or 50x mode and enable or disable the
high pass filters in either of the voltage or the cur-
rent channels.
During Startup the CS5462 will scan the IGAIN in-
put pin and determine which Program Select out-
put it is connected to and then set the PGA and
HPF’s accordingly.
4.2 Pulse-Rate Output
E1 and E2 pins provide a simple interface from
which signed energy can be accumulated. E1 and
E2 can be set to either stepper motor mode or me-
chanical counter mode. The connectivity of the
FREQ pin determines the pulse output mode and
also the maximum frequency for E1 and E2. Figure
3 below describes the options for E1 and E2.
For all applications FREQ must be connected to
one and only one of the Program Selects outputs
(P1 - P7). The frequency setting chosen using the
above table is equal to the set pulse rate frequency
if and only if a full-scale signal is applied to each
channel. As the input signal decreases the pulse
rate and pulse width will decrease by a percentage
equal to the product of the percentages of full-
scale inputs across each channel. For example, if
if FREQ is connected to P5, the maximum pulse
output rate is 4 Hz. Assuming 500 mV is selected
as full scale on each channel, 400 mV is measured
on current and voltage channels. 400 mV is 80% of
full scale. Since power is the product of current and
voltage the pulse outputs will be 80% * 80% = 64%
of full scale. Since 4 Hz is the set full scale output
rate, pulses should appear on E1 and E2 at a
64% * 4 Hz = 2.56 Hz rate.
4.2.1 Stepper Motor Format.
In stepper motor mode the CS5462 produces alter-
nating pulses on E1 and E2. This pulse format is
designed to directly drive a stepper motor. Each
pin produces active-low pulses with frequency de-
pendent pulse widths. The figure below shows the
frequency and corresponding pulse width for each
option.
IGAIN
500mV
P-P
10x P1
P2
P3
P4
P5
100mV
P-P
50x
500mV
P-P
10x
100mV
P-P
50x
P6
P7
500mV
P-P
10x
100mV
P-P
50x
500mV
P-P
10x
no hpf
no hpf
hpf both
hpf both
hpf Ich
hpf Ich
hpf Vch
Figure 2. PGA Settings
FREQ
0.25 Hz / Step P1
P2
P3
P4
P5
0.5 Hz / Step
1 Hz / Step
2 Hz / Step
4 Hz / Step
P6
P7
2 Hz / mech cnt
16 Hz / mech cnt
Figure 3. Pulse Output Settings
0.25 Hz 0.5 Hz
250 m s 250 m s P ulse W idth
Frequency
P1 P 2
FRE Q
connected to:
1 Hz 2 Hz
250 m s 250 m s
P3 P 4
4 Hz
125 m s
P5
E1
pulse width
E2