MCP3909 Microchip Technology, MCP3909 Datasheet - Page 20

• Manufacturer Part Number: MCP3909
• Description: Energy Metering IC with SPI Interface and Active Power Pulse Output
• Manufacturer: Microchip Technology

MCP3909
The
integration times and, thus, higher frequencies. The
output frequency value can be calculated with the
following equation:
EQUATION 4-2:
The constant HF
digital settings with the
The detailed timings of the output pulses are described
in the Timing Characteristics table (see Section 1.0
“Electrical Characteristics” and
TABLE 4-3:
DS22025A-page 20
Where:
F2
0
0
0
0
1
1
1
1
V
HF
REF
high-frequency
V
V
HF
G
C
0
1
OUT
=
=
=
=
=
F1
0
0
1
1
0
0
1
1
(
Hz
the RMS differential voltage on Channel 0
the RMS differential voltage on Channel 1
the PGA gain on Channel 0 (current
channel)
the frequency constant selected
the voltage reference
C
)
F0
OUTPUT FREQUENCY CONSTANT HF
0
1
0
1
0
1
0
1
depends on the F
=
8.06 V
--------------------------------------------------------------- -
ACTIVE POWER HF
FREQUENCY OUTPUT
EQUATION
Table
output
2048 x F
×
128 x F
64 x F
32 x F
16 x F
64 x F
32 x F
16 x F
4-3.
HF
0
(
V
×
C
HF
REF
V
Figure
C
C
C
C
C
C
1
C
C
OUT
×
)
2
OUT0
G
×
1-1).
HF
has
and F
C
OUT
MCLK/2
MCLK/2
MCLK/2
MCLK/2
MCLK/2
MCLK/2
MCLK/2
MCLK/2
HF
lower
OUT1
C
(Hz)
15
15
15
16
16
16
16
7
4.8.1
The MCP3909 also includes, on each output
frequency, a no-load threshold circuit that will eliminate
any creep effects in the meter. The outputs will not
show any pulse if the output frequency falls below the
no-load threshold. This threshold only applies to the
pulse outputs and does not gate any serial data coming
from either the A/D output or the multiplier output. The
minimum output frequency on F
equal to 0.0015% of the maximum output frequency
(respectively F
selections (see
F2, F1, F0 = 011. In this last configuration, the no-load
threshold feature is disabled. The selection of F
determine the start-up current load. In order to respect
the IEC standards requirements, the meter will have to
be designed to allow start-up currents compatible with
the standards by choosing the FC value matching
these
information on no-load threshold, startup current and
other meter design points, refer to AN994, "IEC Com-
pliant Active Energy Meter Design Using The
MCP3905/6”, (DS00994).
C
(MCLK = 3.58 MHz)
FOR HF
27968.75
HF
109.25
109.25
109.25
219.51
219.51
219.51
219.51
requirements.
C
(Hz)
MINIMAL OUTPUT FREQUENCY
FOR NO-LOAD THRESHOLD
OUT
C
Table 4-2
and HF
(V
REF
C
© 2006 Microchip Technology Inc.
For
HF
= 2.4V)
) for each of the F2, F1 and F0
and
OUT
full-scale AC Inputs
Table
additional
Frequency (Hz) with
OUT0/1
6070.12
27.21
27.21
27.21
47.42
47.42
47.42
47.42
4-3); except when
and HF
applications
OUT
C
will
is