Datasheet

Data Sheet ADE7953
Rev. B | Page 47 of 72
INDICATION OF POWER DIRECTION
The ADE7953 includes sign indication on the active and reactive
energy measurements. Sign indication allows positive and nega-
tive energy to be identified and billed separately if required. It
also helps detect a miswiring condition. This feature is available
on both Current Channel A and Current Channel B. Power
direction information is available on both a dedicated output
pin (
REVP
) and via a set of internal registers and interrupts (see
the Reverse Power section and the Sign Indication section).
REVERSE POWER
The
REVP
pin (Pin 20) on the ADE7953 provides a reverse
power indicator. This pin can be configured to provide polarity
information about the active or reactive power on Current
Channel A or Current Channel B. The
REVP
output is high by
default and goes low if the angle between the voltage and current
input is greater than 90°.
REVP
is unlatched and, therefore,
returns high when the reverse power condition is no longer
true. Changes to the
REVP
output pin occur synchronously
to the falling edge of the CF1 pin by default (see Figure 65).
The measurement and channel indicated by the
REVP
pin are
selected by the configuration of the CF output. By default, the
REVP
pin is configured to output synchronous to CF1 and
represents the measurement selected on CF1 using the CF1SEL
bits in the CFMODE register (Address 0x107). By default, this
measurement is the active power on Current Channel A. If the
CF1SEL bits are set to 0x0001, the
REVP
pin indicates the polarity
of the reactive power on Current Channel A. The
REVP
indicator
can be configured to output based on CF2 by setting the REVP_CF
bit in the CONFIG register (Address 0x102). In this configura-
tion, the CF2SEL bits in the CFMODE register determine the
measurement represented on the
REVP
output. If the selected
CF pin is configured to output another measurement, such as
apparent power or IRMS, the
REVP
output is disabled.
To improve the visibility of a reverse polarity condition if an
LED light is used, a 1 Hz pulse mode is available on the
REVP
pin. In this mode, the
REVP
output pin is low by default and
outputs a 1 Hz pulse if the reverse polarity condition is true.
This pulse has a 50% duty cycle. Similar to normal mode, this
mode is also unlatched, and the
REVP
output returns high when
the reverse polarity is no longer true. To enable the
REVP
pulse
mode, the REVP_PULSE bit in the CONFIG register (Address
0x102) should be set to 1.
The
REVP
output pin is disabled in the corresponding no-load
condition. For example, if the reverse polarity information for
Current Channel A active power is present on the
REVP
pin and
the active energy on Current Channel A is in the no-load condi-
tion, the
REVP
output is disabled and held in its current state.
SIGN INDICATION
The ADE7953 includes four sign indication bits that indicate the
polarity of the active power on Current Channel A (APSIGN_A),
the active power on Current Channel B (APSIGN_B), the
reactive power on Current Channel A (VARSIGN_A), and the
reactive power on Current Channel B (VARSIGN_B). These bits
are located in the ACCMODE register (Address 0x201 and
Address 0x301). All four bits are unlatched and read only. A low
reading (0) on any of these bits indicates that the corresponding
power reading is positive; a high reading (1) indicates that the
corresponding power reading is negative. These bits are enabled
by default and are disabled in the corresponding no-load
condition.
In addition to the sign indication bits, the ADE7953 also includes
four sign indication interrupts. If enabled, these interrupts cause
the
IRQ
pin to go low when the polarity of the power changes.
The interrupts are triggered on both positive-to-negative and
negative-to-positive polarity changes. These interrupts are dis-
abled by default and can be enabled by setting the APSIGN_A
and VARSIGN_A bits in the IRQENA register (Address 0x22C
and Address 0x32C), and the APSIGN_B and VARSIGN_B bits
in the IRQENB register (Address 0x22F and Address 0x32F).
See the ADE7953 Interrupts section.
Note that in absolute or positive-only accumulation mode, these
bits are fixed at 0. See the Active Energy Accumulation Modes
section and the Reactive Energy Accumulation Modes section.
CF1
ENTER
REVERSE
CONDITION
REVP
CURRENT AND
VOLTAGE
INPUTS
EXIT
REVERSE
CONDITION
REVP
HIGH
09320-034
REVP
LOW
Figure 65.
REVP
Output