ISL12027 Intersil Corporation, ISL12027 Datasheet - Page 13

• Manufacturer Part Number: ISL12027
• Manufacturer: Intersil Corporation

prevent write operations to one of eight segments of the
array. The partitions are described in Table 3.
Oscillator Compensation Registers
There are two trimming options.
These registers are non-volatile. The combination of analog
and digital trimming can give up to -64 to +110ppm of total
adjustment.
ATR Register - ATR5, ATR4, ATR3, ATR2, ATR1,
ATR0: Analog Trimming Register
Six analog trimming bits, ATR0 to ATR5, are provided in
order to adjust the on-chip load capacitance value for
frequency compensation of the RTC. Each bit has a different
weight for capacitance adjustment. For example, using a
Citizen CFS-206 crystal with different ATR bit combinations
provides an estimated ppm adjustment range from -34 to
+80ppm to the nominal frequency compensation.
The effective on-chip series load capacitance, C
ranges from 4.5pF to 20.25pF with a mid-scale value of
12.5pF (default). C
controlled capacitors, C
0
0
0
0
1
1
1
1
- ATR. Analog Trimming Register
- DTR. Digital Trimming Register
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
X1
X2
FIGURE 12. DIAGRAM OF ATR
PROTECTED ADDRESSES
LOAD
C
C
X1
X2
X1
None (Default)
180
100
000
000
000
is changed via two digitally
000
000
TABLE 3.
ISL12027
and C
h
h
h
h
h
h
h
13
– 1FF
– 1FF
– 1FF
– 03F
– 07F
– 0FF
– 1FF
X2
h
h
h
h
h
h
h
OSCILLATOR
, connected from the X1
CRYSTAL
ARRAY LOCK
First 16 Pages
First 4 Pages
First 8 Pages
Upper 1/4
Upper 1/2
Full Array
Full Array
LOAD
None
,
ISL12027
and X2 pins to ground (see Figure 12). The value of C
C
The effective series load capacitance is the combination of
C
For example, C
C
20.25pF. The entire range for the series combination of load
capacitance goes from 4.5pF to 20.25pF in 0.25pF steps.
Note that these are typical values.
DTR Register - DTR2, DTR1, DTR0: Digital
Trimming Register
The digital trimming Bits DTR2, DTR1 and DTR0 adjust the
number of counts per second and average the ppm error to
achieve better accuracy.
DTR2 is a sign bit. DTR2 = 0 means frequency
compensation is >0. DTR2 = 1 means frequency
compensation is <0.
DTR1 and DTR0 are scale bits. DTR1 gives 10ppm
adjustment and DTR0 gives 20ppm adjustment.
A range from -30ppm to +30ppm can be represented by
using three bits above.
PWR Register: SBIB, BSW, VTS2, VTS1, VTS0
SBIB: Serial Bus Interface (Enable)
The serial bus can be disabled in battery backup mode by
setting this bit to “1”. This will minimize power drain on the
battery. The Serial Interface can be enabled in battery
backup mode by setting this bit to “0” (default is “0”). See
Reset and Power Control section.
C LOAD
C LOAD
C
X2
X1
LOAD
X
DTR2
=
is given by the following formula:
and C
0
0
0
0
1
1
1
1
(
16 b5
(ATR = 100000) = 4.5pF, and C
=
=
DTR REGISTER
⋅
---------------------------------- -




TABLE 4. DIGITAL TRIMMING REGISTERS
16 b5
---------------------------------------------------------------------------------------------------------------------------- -
X2
---------- -
C
1
X1
+
:
⋅
DTR1
8 b4
1
+
LOAD
0
1
0
1
0
1
0
1
⋅
---------- -
C
+
1
8 b4
X2
+
⋅
4 b3


(ATR = 00000) = 12.5pF,
⋅
+
DTR0
4 b3
+
⋅
0
0
1
1
0
0
1
1
2 b2
⋅
+
2 b2
2
+
⋅
1 b1
ESTIMATED FREQUENCY
⋅
+
1 b1
LOAD
+
⋅
0.5 b0
+
⋅
(ATR = 011111) =
0.5 b0
PPM
+10
+20
+30
-10
-20
-30
0
0
+
⋅
9
)pF
+
April 17, 2006
9
 pF

X1
FN8232.3
and