APPENDIX C MOUNTING PRECAUTIONS
AP-C-2
Seiko Epson Corporation
S1C33L26 TECHNICAL MANUAL
Reset circuit
• The reset signal input to the #RESET pin when power is turned on will vary, depending on various factors,
such as power supply start-up time, components used, and circuit board patterns. Constants such as capaci-
tance and resistance should be determined through testing with real-world products.
• Components such as capacitors and resistors connected to the #RESET pin should have the shortest connec-
tions possible to prevent noise-induced resets.
Power supply circuit
Sudden power supply fluctuations due to noise will cause malfunctions. Consider the following issues.
(1) Connections from the power supply to the LV
DD
, HV
DD
, PLLV
DD
, AV
DD
, PLLV
SS
, and V
SS
pins should be
implemented via the shortest, thickest patterns possible. In particular, the power supply for AV
DD
affects A/
D conversion precision.
(2) If a bypass capacitor is connected between
*
V
DD
and V
SS
, connections between the
*
V
DD
and V
SS
pins
should be as short as possible.
*
V
DD
V
SS
Bypass capacitor connection example
*
V
DD
V
SS
A/D Converter
• When the A/D converter is not used, the power supply pin AV
DD
for the analog system should be connected
to HV
DD
.
Signal line location
• To prevent electromagnetically-induced noise arising from mutual induction, large-current signal lines should
not be positioned close to circuits susceptible to noise, such as oscillators.
• Locating signal lines in parallel over significant distances or crossing signal lines operating at high speed will
cause malfunctions due to noise generated by mutual interference. Specifically, avoid positioning crossing
signal lines operating at high speed close to circuits susceptible to noise, such as oscillators and analog in-
puts.
RTCCLKI, MCLKI
RTCCLKO, MCLKO
V
SS
Large current signal line
High-speed signal line
Prohibited pattern
USB
The I/O block of the USB Function Controller incorporated in this chip has the following features:
The DP and DM pins can be connected directly to the USB connector.
The VBUS level is detected by means of a 2/3 resistive division internally in the chip, thus allowing for direct
input of a 5 V-level signal.
The receiver does not enter a floating state even when the USB cable is disconnected from the USB connec-
tor. When the USB cable is disconnected, the VBUS pin is tied to V
SS
, so that leakage current will be the only
source that drains power in the USB I/O block.