ISL12020MIRZ Intersil, ISL12020MIRZ Datasheet - Page 20

• Manufacturer Part Number: ISL12020MIRZ
• Description: IC RTC/CALENDAR TEMP SNSR 20-DFN
• Manufacturer: Intersil
• Type: Clock/Calendarr

Specifications of ISL12020MIRZ

• Memory Size: 1K (128 x 8)
• Time Format: HH:MM:SS (12/24 hr)
• Date Format: YY-MM-DD-dd
• Interface: I²C, 2-Wire Serial
• Voltage - Supply: 2.7 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 20-DFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

FREQUENCY OF TEMPERATURE SENSING AND
CORRECTION BIT (BTSR)
This bit controls the frequency of Temp Sensing and
Correction. BTSR = 0 default mode is every 10 minutes,
BTSR = 1 is every 1.0 minute. Note that BTSE has to be
enabled in both cases. See Table 15.
The temperature measurement conversion time is the
same for battery mode as for V
22ms. The battery mode current will increase during
this conversion time to typically 68µA. The average
increase in battery current is much lower than this due
to the small duty cycle of the ON-time versus OFF-time
for the conversion.
To figure the average increase in battery current, we take
the change in current times the duty cycle. For the
1 minute temperature period the average current is as
shown in Equation 1:
For the 10 minute temperature period the average
current is as shown in Equation 2:
If the application has a stable temperature environment
that doesn’t change quickly, the 10 minute option will
work well and the backup battery lifetime impact is
minimized. If quick temperature variations are expected
(multiple cycles of more than 10° within an hour), then
the 1 minute option should be considered and the slightly
higher battery current figured into overall battery life.
GAIN FACTOR OF AT BIT (BETA<4:0>)
Beta is specified to take care of the Cm variations of the
crystal. Most crystals specify Cm around 2.2fF. For
example, if Cm > 2.2fF, the actual AT steps may reduce
from 1ppm/step to approximately 0.80ppm/step. Beta
is then used to adjust for this variation and restore the
step size to 1ppm/step.
BETA values are limited in the range from 01000 to
11111 as shown in Table 16
is tested at two AT settings in Equation 3:
where:
AT(max) = F
ΔI
ΔI
TABLE 15. FREQUENCY OF TEMPERATURE SENSING
BETA VALUES
BAT
BAT
=
=
0.022s
----------------- -
0.022s
----------------- -
BTSE
600s
60s
0
0
1
1
AND CORRECTION BIT
OUT
=
×
×
68μA
68μA
(
AT max
in ppm (at AT = 00H) and
(
=
=
250nA
25nA
) AT min
–
20
BTSR
.
(
To use Table 16, the device
0
1
0
1
DD
)
)/63
mode, approximately
BATTERY MODE
TC PERIOD IN
10 Minutes
1 Minute
OFF
OFF
(EQ. 1)
(EQ. 2)
(EQ. 3)
ISL12020M
AT(min) = F
The BETA VALUES result is indexed in the right hand
column and the resulting Beta factor (for the register) is
in the same row in the left column.
The ISL12020M has a preset BETA value corresponding
to the crystal in the module. This value is recalled on
initial power-up and should never be changed for
best temperature compensation performance,
although the user may override this preset value if
so desired.
The value for BETA should only be changed while the TSE
(Temp Sense Enable) bit is “0”. The procedure for writing
the BETA register involves two steps. First, write the new
value of BETA with TSE = 0. Then write the same value of
BETA with TSE = 1. This will insure the next temp sense
cycle will use the new BETA value
Final Analog Trimming Register (FATR)
This register shows the final setting of AT after
temperature correction. It is read-only; the user cannot
overwrite a value to this register. This value is accessible
as a means of monitoring the temperature compensation
function. See Tables 17 and 18 (for values).
BETA<4:0>
01000
00111
00110
00101
00100
00011
00010
00001
00000
10000
10001
10010
10011
10100
10101
10110
10111
11000
11001
11010
11011
11100
11101
11110
11111
OUT
TABLE 16. BETA VALUES
in ppm (at AT = 3FH).
AT STEP ADJUSTMENT
.
0.5000
0.5625
0.6250
0.6875
0.7500
0.8125
0.8750
0.9375
1.0000
1.0625
1.1250
1.1875
1.2500
1.3125
1.3750
1.4375
1.5000
1.5625
1.6250
1.6875
1.7500
1.8125
1.8750
1.9375
2.0000
February 11, 2010
FN6667.4