71m6511h-igtr Maxim Integrated Products, Inc., 71m6511h-igtr Datasheet - Page 53

• Manufacturer Part Number: 71m6511h-igtr
• Description: Single-phase Energy Meter Ic
• Manufacturer: Maxim Integrated Products, Inc.

If temperature compensation or accurate reading of the die temperature is required, alternate multiplexer cycles have to be
inserted in between the regular cycles. This is done under MPU firmware control by asserting the MUX_ALT bit whenever
necessary. Since die temperature usually changes very slowly, alternate multiplexer cycles have to be inserted very
infrequently. Usually, an alternate multiplexer cycle is inserted once for every accumulation period, i.e. after each XFER_BUSY
interrupt. This sequence is shown in Figure 22.
This sequence has the disadvantage that the alternate multiplexer cycle is always operated with positive connection.
Consequently, DC offset will appear on the temperature measurement, which will decrease the accuracy of this measurement
and thus cause temperature reading and compensation to be less accurate.
The sequence shown in Figure 23 uses the CHOP_EN bits to control the chopper polarity after each XFER_BUSY interrupt.
CHOP_EN is controlled to alternate between 10 (positive) and 01 (reversed) for the first multiplexer cycle following each
Page: 53 of 95
alt. MUX
Positive
cycle
cycle 1
Positive
XFER_BUSY interrupt
MUX
Accumulation Interval m
CE_BUSY interrupt
versed
cycle 2
MUX
Re-
XFER_BUSY interrupt
Chop Polarity
Accumulation Interval m
CE_BUSY interrupt
MUX_ALT
versed
cycle 2
Chop Polarity
MUX
Re-
(falling edge)
(falling edge)
Positive
cycle 3
MUX
Positive
cycle 3
MUX
versed
cycle n
Figure 22: Sequence with Alternate Multiplexer Cycles
MUX
Re-
Figure 21: Chop Polarity w/ Automatic Chopping
cycle n
versed
© 2005-2007 TERIDIAN Semiconductor Corporation
MUX
Re-
alt. MUX
Positive
cycle
Positive
cycle 1
Accumulation Interval m+1
MUX
versed
Re-
Accumulation Interval m+1
versed
Re-
Positive
Positive
Single-Phase Energy Meter IC
cycle n
versed
MUX
Re-
cycle n
versed
MUX
Re-
71M6511/71M6511H
alt. MUX
Positive
cycle
Positive
DATA SHEET
cycle 1
Accumulation Interval m+2
MUX
versed
Re-
Accumulation Interval m+2
versed
Re-
Positive
Positive
AUGUST 2007
V2.6