71M6545 MAXIM [Maxim Integrated Products], 71M6545 Datasheet - Page 53

• Manufacturer Part Number: 71M6545
• Description: Four-Quadrant Metering, Phase Metrology Processors Flash/RAM Size
• Manufacturer: MAXIM [Maxim Integrated Products]

The temperature sensor can be used to compensate for the frequency variation of the crystal, during ac
power outages, provided the VBAT_RTC voltage is within specification (supplied by a battery). See
2.5.4.4 RTC Temperature Compensation
In MSN mode, the temperature sensor is awakened on command from the MPU by setting the
PDS_6545_009
2.5.5 71M6545/H Temperature Sensor
The 71M6545/H includes an on-chip temperature sensor for determining the temperature of its
bandgap reference. The primary use of the temperature data is to determine the magnitude of
compensation required to offset the thermal drift in the system for the compensation of current, voltage
and energy measurement and the RTC. See
see
TEMP_START (I/O RAM 0x28B4[6]) control bit. During power outages and while operating from
VBAT_RTC power, it is awakened at a regular rate set by TEMP_PER[2:0] (I/O RAM 0x28A0[2:0]).
The result of the temperature measurement can be read from the two I/O RAM locations STEMP[10:3]
(I/O RAM 0x2881) and STEMP[2:0] (I/O RAM 0x2882[7:5]). Note that both of these I/O RAM locations must
be read and properly combined to form the STEMP[10:0] 11-bit value (see STEMP in
resulting 11-bit value is in 2’s complement form and ranges from -1024 to +1023 (decimal). The equations
below are used to calculate the sensed temperature from the 11-bit STEMP[10:0] reading.
For the 71M6545 in MSN Mode (with TEMP_PWR = 1):
For the temperature sensors in the 71M6545H:
If STEMP ≤ 0:
If STEMP > 0:
The TEMP_85[10:0] trim fuses are read from the Info Page. See
only)
Table 43
v1.0
RTC_TMIN[5:0] 289E[5:0]
RTC_THR[4:0]
Name
2.5.4.4 RTC Temperature Compensation
on page
measurement may not finish. In this case, firmware may complete the measurement by selecting
V3P3D (TEMP_PWR = 1).
If TEMP_PWR selects VBAT_RTC when the battery is nearly discharged, the temperature
shows the I/O RAM registers used for temperature and battery measurement.
98
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for information on how to read the 71M6545H trim fuses.
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Location Rst
289F[4:0]
© 2008–2011 Teridian Semiconductor Corporation
63 ∙ ����������
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0
0
Temp
Wk
0
0
(
on page 51.
+ 0.00218 ∙ ������������
R/W The target minutes register. See below.
R/W
o
Dir
4.5 Metrology Temperature Compensation
C
)
on page 51.
=
The target hours register. The RTC_T interrupt occurs
when RTC_MIN[5:0] becomes equal to RTC_TMIN[5:0]
and RTC_HR[4:0] becomes equal to RTC_THR[4:0].
Description
. 0
325
⋅
STEMP
2
− 0.609 ∙ ������������ + 64.4
2
5.3 Reading the Info Page (71M6545H
− 0.609 ∙ ������������ + 64.4
+
22
Data Sheet 71M6545/H
Table
on page 74. Also
43). The
53