cs5461 Cirrus Logic, Inc., cs5461 Datasheet - Page 40

• Manufacturer Part Number: cs5461
• Description: Single-phase, Bidirectional Power/energy Ic
• Manufacturer: Cirrus Logic, Inc.

8. BASIC APPLICATION CIRCUITS
Figure 14 shows the CS5461 connected to a service
to measure power in a single-phase 2-wire system
while operating in a single supply configuration.
Note that in this diagram the shunt resistor used to
monitor the line current is connected on the “Line”
(hot) side of the power mains. In most residential
power metering applications, the power meter’s
current-sense shunt resistor is intentionally placed
on the hot side of the power mains in order to detect
a subscriber’s attempt to steal power. In this type of
shunt-resistor configuration, the common-mode
level of the CS5461 must be referenced to the hot
side of the power line; which means the com-
mon-mode potential of the CS5461 will typically
oscillate to very high voltage levels with respect to
earth ground potential. If digital communication
networks require that the CMOS-level digital inter-
face be referenced to an earth ground, the serial in-
40
Figure 14. Typical Connection Diagram (One-Phase 2-Wire, Direct Connect to
N
R
2
To Service
120 VAC
R
1
L
470 nF
R
Shunt
500 Ω
R
R
I-
I+
R
V-
C
V+
C
I+
100 µF
500
terface pins on the CS5461 must be isolated from
the external digital interface.
Figure 15 shows the same single-phase two-wire
system with complete isolation from the power
lines. This isolation is achieved using three trans-
formers: a general purpose transformer to supply
the on-board DC power; a high-precision, low im-
pedance voltage transformer, with very little
roll-off/phase-delay, to measure voltage; and a cur-
rent transformer to sense the line current. Because
the CS5461 is not directly connected to the power
mains, no isolation is necessary on the CS5461’s
digital interface.
Figure 16 shows a single-phase 3-wire system. In
many 3-wire residential power systems within the
United States, only the two line terminals are avail-
able (neutral is not available). Figure 17 shows the
CS5461 configured to meter a three-wire system
with no neutral available.
0.1 µF
0.1 µF
10
15
16
12
11
9
VIN+
VIN-
IIN-
IIN+
VREFIN
VREFOUT
VA+
14
VA-
13
CS5461
10 Ω
DGND
CPUCLK
PFMON
RESET
XOUT
EOUT
SCLK
4
EDIR
VD+
SDO
XIN
SDI
INT
CS
3
5 kΩ
22
21
17
2
1
24
19
7
23
6
5
20
0.1 µF
Mech. Counter
Stepper Motor
2.5 MHz to
20 MHz
or
Optional
Source
10 k Ω
Clock
Interface
Serial
Data
CS5461
DS546F2