ISL12023 Datasheet, PDF (16/28 Pages) Intersil Corporation – Low Power RTC with Battery-Backed SRAM and Embedded Temp Compensation ±5ppm with Auto Daylight Saving

ISL12023
Initial AT and DT Setting Register (ITRO)
These bits are used to trim the initial error (at room
temperature) of the crystal. Both Digital Trimming (DT) and
Analog Trimming (AT) methods are available. The digital
trimming uses clock pulse skipping and insertion for
frequency adjustment. Analog trimming uses load
capacitance adjustment to pull the oscillator frequency. A
range of +62.5ppm to -61.5ppm is possible with combined
digital and analog trimming.
AGING AND INITIAL TRIM DIGITAL TRIMMING BITS
(IDTR0<1:0>)
These bits allow ±30.5ppm initial trimming range for the
crystal frequency. This is meant to be a coarse adjustment if
the range needed is outside that of the IATR control. See
Table 10. The IDTR0 register should only be changed while
the TSE (Temp Sense Enable) bit is “0”.
TABLE 10. IDTR0 TRIMMING RANGE
IDTR01
IDTR00
TRIMMING RANGE
0
0
Default/Disabled
0
1
+30.5ppm
1
0
0ppm
1
1
-30.5ppm
AGING AND INITIAL ANALOG TRIMMING BITS
(IATR0<5:0>)
The analog trimming register allows +32ppm to -31ppm
adjustment in 1ppm/bit increments. This enables fine frequency
adjustment for trimming initial crystal accuracy error or to
correct for aging drift. The IATR0 register should only be
changed while the TSE (Temp Sense Enable) bit is “0”.
TABLE 11. INITIAL AT AND DT SETTING REGISTER
ADDR 7
6
5
4
3
2
1
0
0Bh IDTR01 IDTR00 IATR05 IATR04 IATR03 IATR02 IATR01 IATR00
Note that setting the IATR to the lowest settings (-31ppm)
with the default 32kHz output can cause the oscillator
frequency to become unstable on power-up. The lowest
settings for IATR should be avoided to insure oscillator
frequency integrity.
TABLE 12. IATRO TRIMMING RANGE
TRIMMING
IATR05 IATR04 IATR03 IATR02 IATR01 IATR00 RANGE
0
0
0
0
0
0
+32
0
0
0
0
0
1
+31
0
0
0
0
1
0
+30
0
0
0
0
1
1
+29
0
0
0
1
0
0
+28
0
0
0
1
0
1
+27
0
0
0
1
1
0
+26
0
0
0
1
1
1
+25
TABLE 12. IATRO TRIMMING RANGE (Continued)
TRIMMING
IATR05 IATR04 IATR03 IATR02 IATR01 IATR00 RANGE
0
0
1
0
0
0
+24
0
0
1
0
0
1
+23
0
0
1
0
1
0
+22
0
0
1
0
1
1
+21
0
0
1
1
0
0
+20
0
0
1
1
0
1
+19
0
0
1
1
1
0
+18
0
0
1
1
1
1
+17
0
1
0
0
0
0
+16
0
1
0
0
0
1
+15
0
1
0
0
1
0
+14
0
1
0
0
1
1
+13
0
1
0
1
0
0
+12
0
1
0
1
0
1
+11
0
1
0
1
1
0
+10
0
1
0
1
1
1
+9
0
1
1
0
0
0
+8
0
1
1
0
0
1
+7
0
1
1
0
1
0
+6
0
1
1
0
1
1
+5
0
1
1
1
0
0
+4
0
1
1
1
0
1
+3
0
1
1
1
1
0
+2
0
1
1
1
1
1
+1
1
0
0
0
0
0
0
1
0
0
0
0
1
-1
1
0
0
0
1
0
-2
1
0
0
0
1
1
-3
1
0
0
1
0
0
-4
1
0
0
1
0
1
-5
1
0
0
1
1
0
-6
1
0
0
1
1
1
-7
1
0
1
0
0
0
-8
1
0
1
0
0
1
-9
1
0
1
0
1
0
-10
1
0
1
0
1
1
-11
1
0
1
1
0
0
-12
1
0
1
1
0
1
-13
1
0
1
1
1
0
-14
1
0
1
1
1
1
-15
1
1
0
0
0
0
-16
1
1
0
0
0
1
-17
1
1
0
0
1
0
-18
1
1
0
0
1
1
-19
1
1
0
1
0
0
-20
1
1
0
1
0
1
-21
1
1
0
1
1
0
-22
1
1
0
1
1
1
-23
1
1
1
0
0
0
-24
1
1
1
0
0
1
-25
1
1
1
0
1
0
-26
1
1
1
0
1
1
-27
16
FN6682.2
June 24, 2009