71M6545 Datasheet, PDF (19/134 Pages) Maxim Integrated Products – Four-Quadrant Metering, Phase Metrology Processors Flash/RAM Size

PDS_6545_009
Data Sheet 71M6545/H
Table 3 summarizes the I/O RAM registers used for configuring the multiplexer, signals pins, and ADC.
All listed registers are 0 after reset and wake from SLP mode, and are readable and writable.
Table 3: Multiplexer and ADC Configuration Bits
Name
Location Description
MUX0_SEL[3:0] 2105[3:0] Selects the ADC input converted during time slot 0.
MUX1_SEL[3:0] 2105[7:4] Selects the ADC input converted during time slot 1.
MUX2_SEL[3:0] 2104[3:0] Selects the ADC input converted during time slot 2.
MUX3_SEL[3:0] 2104[7:4] Selects the ADC input converted during time slot 3.
MUX4_SEL[3:0] 2103[3:0] Selects the ADC input converted during time slot 4.
MUX5_SEL[3:0] 2103[7:4] Selects the ADC input converted during time slot 5.
MUX6_SEL[3:0] 2102[3:0] Selects the ADC input converted during time slot 6.
MUX7_SEL[3:0] 2102[7:0] Selects the ADC input converted during time slot 7.
MUX8_SEL[3:0] 2101[3:0] Selects the ADC input converted during time slot 8.
MUX9_SEL[3:0] 2101[7:0] Selects the ADC input converted during time slot 9.
MUX10_SEL[3:0] 2100[3:0] Selects the ADC input converted during time slot 10.
ADC_DIV
2200[5] Controls the rate of the ADC and FIR clocks.
MUX_DIV[3:0] 2100[7:4] The number of ADC time slots in each multiplexer frame (maximum = 11).
PLL_FAST
FIR_LEN[1:0]
2200[4] Controls the speed of the PLL and MCK.
210C[2:1] Determines the number of ADC cycles in the ADC decimation FIR filter.
DIFF0_E
210C[4] Enables the differential configuration for analog input pins IADC0-IADC1 .
DIFF2_E
210C[5] Enables the differential configuration for analog input pins IADC2-IADC3 .
DIFF4_E
210C[6] Enables the differential configuration for analog input pins IADC4-IADC5 .
DIFF6_E
210C[7] Enables the differential configuration for analog input pins IADC6-IADC7 .
RMT2_E
2709[3]
Enables the remote sensor interface transforming pins IADC2-IADC3 into a digital
interface for communications with a 71M6xx3 sensor.
RMT4_E
2709[4]
Enables the remote sensor interface transforming pins IADC4-IADC5 into a digital
interface for communications with a 71M6xx3 sensor.
RMT6_E
2709[5]
Enables the remote sensor interface transforming pins IADC6-IADC7 into a digital
interface for communications with a 71M6xx3 sensor.
PRE_E
2704[5] Enables the 8x pre-amplifier.
Refer to Table 61 starting on page 88 for more complete details about these I/O RAM locations.
2.2.3 Delay Compensation
When measuring the energy of a phase (i.e., Wh and VARh) in a service, the voltage and current for that
phase must be sampled at the same instant. Otherwise, the phase difference, Ф, introduces errors.
φ
=
t_delay
T
⋅ 360^o
= t_delay
⋅
f
⋅ 360^o
Where f is the frequency of the input signal, T = 1/f and t_delay is the sampling delay between current and
voltage.
Traditionally, sampling is accomplished by using two A/D converters per phase (one for voltage and the
other one for current) controlled to sample simultaneously. Teridian’s Single-Converter Technology^®,
however, exploits the 32-bit signal processing capability of its CE to implement “constant delay” all-pass
filters. The all-pass filter corrects for the conversion time difference between the voltage and the
corresponding current samples that are obtained with a single multiplexed A/D converter.
The “constant delay” all-pass filter provides a broad-band delay 360^o - θ, that is precisely matched to the
difference in sample time between the voltage and the current of a given phase. This digital filter does
not affect the amplitude of the signal, but provides a precisely controlled phase response.
The recommended ADC multiplexer sequence samples the current first, immediately followed by
sampling of the corresponding phase voltage, thus the voltage is delayed by a phase angle Ф relative to
the current. The delay compensation implemented in the CE aligns the voltage samples with their
corresponding current samples by first delaying the current samples by one full sample interval (i.e.,
v1.0
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