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Section 11 Realtime Clock (RTC)
SH7751 Group, SH7751R Group
Page 314 of 1128
R01UH0457EJ0301 Rev. 3.01
Sep 24, 2013
This LSI
EXTAL2
XTAL2
XTAL
C
in
C
out
R
f
R
D
Noise filter
C
RTC
R
RTC
3.3 V
VDD-RTC
VSS-RTC
Notes: 1. Select either the C
in
or C
out
side for the frequency adjustment variable capacitor accordin
g
to
requirements such as the adjustment ran
g
e, de
g
ree of stability, etc.
2. Built-in resistance value R
f
(typ. value) = 10 M
Ω
, R
D
(typ. value) = 400 k
Ω
3.
C
in
and C
out
values include floatin
g
capacitance due to the wirin
g
. Take care when usin
g
a solid-
earth board.
4. The crystal oscillation stabilization time depends on the mounted circuit constants, floatin
g
capacitance, etc., and should be decided after consultation with the crystal resonator
manufacturer.
5. Place the crystal resonator and load capacitors C
in
and C
out
as close as possible to the chip.
(Correct oscillation may not be possible if there is externally induced noise in the EXTAL2 and
XTAL2 pins.)
6. Ensure that the crystal resonator connection pin (EXTAL2 and XTAL2) wirin
g
is routed as far away
as possible from other power lines (except GND) and si
g
nal lines.
7. Insert a noise filter in the RTC power supply.
Figure 11.5 Example of Crystal Oscillation Circuit Connection