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4
Precautions on Mounting
<Oscillation Circuit>
Oscillation characteristics change depending on conditions (board pattern, components used, etc.).
In particular, when a crystal oscillator is used, use the oscillator manufacturer's recommended values for
constants such as capacitance.
Disturbances of the oscillation clock due to noise may cause a malfunction. Consider the following points to
prevent this:
(1) Components which are connected to the OSC3, OSC4 terminals, such as oscillators and capacitors, should
be connected in the shortest line.
(2) As shown in the right hand figure, make a V
OSC4 terminals and the components connected to these terminals.
Furthermore, do not use this V
(3) When supplying an external clock to the OSC3 terminal, the clock source should be connected to the OSC3
terminal in the shortest line.
Furthermore, do not connect anything else to the OSC4 terminal.
In order to prevent unstable operation of the oscillation circuit due to current leak between OSC3 and V
please keep enough distance between OSC3 and V
<Power Supply Circuit>
Sudden power supply variation due to noise may cause malfunction. Consider the following points to prevent
this:
(1) The power supply should be connected to the V
as possible.
(2) When connecting between the V
connected as short as possible.
S1C05251 TECHNICAL MANUAL
SS
pattern for any purpose other than the oscillation system.
SS
Sample V
pattern
SS
and V
terminals with a bypass capacitor, the terminals should be
DD
SS
Bypass capacitor connection example
V
DD
V
SS
pattern as large as possible at circumscription of the OSC3,
OSC4
OSC3
V
SS
or other signals on the board pattern.
DD
, V
and V
terminals with patterns as short and large
DD
SS
REF
V
V
EPSON
4 PRECAUTIONS ON MOUNTING
DD
SS
,
DD
17
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