Datasheet

Clock operation M41T93
26/56 DocID12615 Rev 8
As shown in Figure 12, the relationship between oscillator speed and load capacitance is
not linear. When operating on the left end of the curve, small changes in load capacitance
have more effect than when operating on the right end of the curve. For example, at –15 pF,
a 3 pF reduction to –18 pF should result in the part running about 30 ppm faster (from
+65 ppm to +95 ppm). Conversely, at +5 pF, adding 3 pF to get to +8 pF should only slow
the part by about 4 ppm (from –8 ppm to –12 ppm).
3.4.3 Pre-programmed calibration value
Users of the M41T83 in the embedded crystal package have the option of using the factory
programmed analog calibration value (refer to Section 3.16 on page 42).
Figure 11. Crystal accuracy across temperature
AI07888
–160
010203040506070
Fr eq u en cy (p p m )
Temperature °C
80–10–20–30–40
–100
–120
–140
–40
–60
–80
20
0
–20
= –0.036 ppm/ °C
2
± 0.006 ppm/ °C
2
K
ΔF
= K x (T – T
O
)
2
F
T
O
= 25°C ± 5°C
Table 5. Analog calibration values
Addr
Analog
calibration
value
D7 D6 D5 D4 D3 D2 D1 D0
C
XI
, C
XO
C
LOAD
(1)
ACS
(±)
AC6
(16 pF)
AC5
(8 pF)
AC4
(4 pF)
AC3
(2 pF)
AC2
( 1pF)
AC1
(0.5 pF)
AC0
(0.25 pF)
12h
0 pF x 0 0 0 0 0 0 0 25 pF 12.5 pF
3 pF 0 0 0 0 1 1 0 0 28 pF 14 pF
5 pF 0 0 0 1 0 1 0 0 30 pF 15 pF
–7 pF 1 0 0 1 1 1 0 0 18 pF 9 pF
9.75 pF
(2)
0 0 1 0 0 1 1 1 34.75 pF 17.4 pF
–18 pF
(3)
1 1 0 0 1 0 0 0 7 pF 3.5 pF
1. C
LOAD
= 1/(1/C
XI
+ 1/C
XO
)
2. Maximum negative calibration value
3. Maximum positive calibration value