
is1C33L17sPeCifiCations:PreCautionsonMounting
s1C33L17teChniCaLManuaL
ePson
i-9-3
I
Mount
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 connector.
When the USB cable is disconnected, the VBUS pin is tied to VSS, so that leakage current will be the only
source that drains power in the USB I/O block.
PrecautionsonvBus
Be sure to not apply 6 V (max.) or more to the VBUS pin as the IC may be destroyed.
It is especially necessary to suppress overshoot on the input voltage and to prevent the host power source
becoming unstable when the USB cable is plugged into the connector. To do this, connect a 1 F or more
capacitor near the USB connector for decoupling the VBUS signal. Choose a ceramic capacitor for decoupling.
USB connector
VBUS pin
USBVBUS pin
1
F or more
In addition to the above, verify the VBUS state completely on the actual circuit board using an oscilloscope
or other device. Overshoot and other symptoms are more likely to occur when using a long USB cable and
connecting it to the host side connector.
PrecautionsonDPandDM
When designing a printed circuit board, observe the following precautions to ensure that both DP and DM
signals are properly routed:
To prevent signal skew and to stabilize differential impedance, the DP and DM signal lines must be routed
in parallel and in the same length, with the pins and connector connected in the shortest distance possible.
Crossed wiring of these signals should be avoided as much as possible.
The periphery of these signal lines must be enclosed by a GND pattern, and with the GND pattern also
created for the internal layer immediately below that. In particular, the routing of high-speed digital signal
lines parallel to or across these signal lines should be avoided as much as possible.
We recommend that you verify the EYE pattern on the actual circuit board.
Sample EYE Diagram