CHAPTER 5: SUMMARY OF NOTES

5.3 Precautions on Mounting

<Oscillation Circuit>

●Oscillation characteristics change depending on conditions (board pattern, components used, etc.). In particular, when a ceramic oscillator or crystal oscillator is used, use the oscillator manufacturer's recommended values for constants such as capacitance and resistance.

●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 OSC1, OSC2, OSC3 and OSC4 terminals, such as oscillators, resistors and capacitors, should be connected in the shortest line.

(2)As shown in the right hand figure, make a VSS pattern as large as possible at circumscription of the OSC1, OSC2, OSC3 and OSC4 terminals and the components connected to these terminals. Furthermore, do not use this VSS pattern for any purpose other than the oscillation system.

Sample VSS pattern (OSC3)

OSC4

OSC3

VSS

●In order to prevent unstable operation of the oscillation circuit due to current leak between OSC1/ OSC3 and VDD, please keep enough distance between OSC1/OSC3 and VDD or other signals on the board pattern.

<Reset Circuit>

●The power-on reset signal which is input to the RESET terminal changes depending on conditions (power rise time, components used, board pattern, etc.).

Decide the time constant of the capacitor and resistor after enough tests have been completed with the application product.

When the built-in pull-up resistor is added to the RESET terminal by mask option, take into consider- ation dispersion of the resistance for setting the constant.

●In order to prevent any occurrences of unnecessary resetting caused by noise during operating, components such as capacitors and resistors should be connected to the RESET terminal in the shortest line.

<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 VDD and VSS terminals with patterns as short and large as possible.

(2)When connecting between the VDD and VSS terminals with a bypass capacitor, the terminals should be connected as short as possible.

Bypass capacitor connection example

VDD VDD

VSS VSS

(3)Components which are connected to the VD1 and VC1–VC5terminals, such as capacitors, should be connected in the shortest line.

In particular, the VC1–VC5voltages affect the display quality.

●Do not connect anything to the VC1–VC5terminals when the LCD driver is not used.

S1C63558 TECHNICAL MANUAL

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