71M6542F MAXIM [Maxim Integrated Products], 71M6542F Datasheet - Page 132

• Manufacturer Part Number: 71M6542F
• Description: 0.1% Accuracy Over 2000:1 Current Range Energy Meter ICs
• Manufacturer: MAXIM [Maxim Integrated Products]

71M6541D/F/G and 71M6542F/G Data Sheet
5.3.9 Pulse Generation
Table 90
The combination of the CECONFIG PULSE_SLOW and PULSE_FAST bits (CE RAM 0x20[0:1]) controls the
speed of the pulse rate. The default values of 0 and 0 maintain the original pulse rate given by the Kh
equation.
WRATE (CE RAM 0x21) controls the number of pulses that are generated per measured Wh and VARh
quantities. The lower WRATE is, the slower the pulse rate for the measured energy quantity. The metering
constant Kh is derived from WRATE as the amount of energy measured for each pulse. That is, if Kh =
1Wh/pulse, a power applied to the meter of 120 V and 30 A results in one pulse per second. If the load
is 240 V at 150 A, ten pulses per second are generated.
Control is transferred to the MPU for pulse generation if EXT_PULSE = 1 (CE RAM 0x20[5]). In this case,
the pulse rate is determined by APULSEW and APULSER (CE RAM 0x45 and 0x49). The MPU has to
load the source for pulse generation in APULSEW and APULSER to generate pulses. Irrespective of the
EXT_PULSE status, the output pulse rate controlled by APULSEW and APULSER is implemented by the CE
only. By setting EXT_PULSE = 1, the MPU is providing the source for pulse generation. If EXT_PULSE is
0, W0SUM_X (CE RAM 0x85) and VAR0SUM_X (CE RAM 0x89) are the default pulse generation sources. In
this case, creep cannot be controlled since it is an MPU function.
The maximum pulse rate is 3*F
See
The maximum time jitter is 1/6 of the multiplexer cycle period (nominally 67 µs) and is independent of the
number of pulses measured. Thus, if the pulse generator is monitored for one second, the peak jitter is
67 ppm. After 10 seconds, the peak jitter is 6.7 ppm. The average jitter is always zero. If it is attempted
to drive either pulse generator faster than its maximum rate, it simply outputs at its maximum rate without
exhibiting any rollover characteristics. The actual pulse rate, using WSUM as an example, is:
where F
PULSE_SLOW (CE RAM 0x20[0]) and PULSE_FAST (CE RAM 0x20[1]).
Address
0x83
0x82
CE
2.3.6.2 VPULSE and WPULSE
S
describes the CE pulse generation parameters.
= sampling frequency (2520.6 Hz), X = Pulse speed factor derived from the CE variables
MAINEDGE_X
FREQ_X
Name
S
= 7.56 kHz.
The number of edge crossings of the selected voltage in the previous
accumulation interval. Edge crossings are either direction and are
de-bounced.
Description
Fundamental frequency: LSB
Table 89: Other Transfer Variables
RATE
for details on how to adjust the timing of the output pulses.
=
WRATE
⋅
WSUM
2
46
LSB
⋅
F
S
⋅
X
≡
≡
Hz
2520
2520
,
2
2
32
32
6 .
6 .
Hz
Hz
≈
≈
. 0
. 0
509
587
⋅
⋅
10
10
−
−
6
6
Hz(for Local)
Hz(for Remote)