CS5460A
complete isolation from the power lines. This isola-
tion is achieved using three transformers. One
transformer is a general-purpose voltage trans-
former, used to supply the on-board DC power to
the CS5460A. A second transformer is a high-pre-
cision, low-impedance voltage transformer (often
called a ‘potential transformer’) with very little
roll-off/phase delay, even at the higher harmonics.
A current transformer is then used to sense the line
current. A burden resistor placed across the sec-
ondary of the current transformer creates the cur-
rent-sense voltage signal, for the CS5460A’s
current channel inputs. Because the CS5460A is
not directly connected to the power mains, isola-
tion is not required for the CS5460A’s digital inter-
face.
Figure 8 shows the CS5460A configured to mea-
sure power in a single-phase 3-wire system. In
many 3-wire residential power systems within the
United States, only the two Line terminals are
available (neutral is not available). Figure 9 shows
how the CS5460A can be configured to meter a
3-wire system when no neutral is available.
Ω
Ω
5 k
10 k
120 VAC
N
L
Ω
10
500
Ω
500
Ω
0.1 µF
100 µF
0.1 µF
+
470 nF
14
3
VA+
VD+
CS5460A
17
2
PFMON
CPUCLK
XOUT
9
VIN+
* *
CV+
1
2.5 MHz to
20 MHz
* *
CVdiff
R
R
1
2
* *
CV-
*
RV-
Optional
Clock
Source
10
24
VIN-
IIN-
XIN
15
*
* *
CI-
RI-
19
7
RESET
NOTE: Current channel
input measures voltage
(just like voltage input).
* *
C Idiff
RShunt
CS
SDI
Serial
Data
23
6
*
RI+
SDO
SCLK
INT
Interface
16
5
IIN+
20
* *
CI+
12
11
VREFIN
22
21
EDIR
VREFOUT
EOUT
0.1 µF
VA-
13
DGND
4
Mech. Counter
or
Stepper Motor
To Service
* Refer to Input Protection
** Refer to Input Filtering
Figure 6. Typical Connection Diagram (One-Phase 2-Wire, Direct Connect to Power Line)
17
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