THE DESIGN CYCLE
Pins 11 and 12 are used for power management.
The CP2103's USB function controller supports USB
Suspend and Resume signals, and extends the USB power
management functionality to external devices via the
active high SUSPEND and active low /SUSPEND pins. The
CP2103 enters Suspend mode when a suspend signal is
active on the bus. An example of how the SUSPEND
signals are used can be seen in Schematic 1. Note that the
SP3243EU's /SHUTDOWN pin is under the control of the
/SUSPEND pin. When the CP2103 goes into Suspend
mode, it also shuts down the SP3243EU. The CP2103
exits Suspend mode upon receiving Resume signaling on
the bus. A USB Reset signal or a
device reset will also terminate
VBUS, D+, and D- are standard
USB signals. The SP0503BAHT
attached to these signals is a trio
of avalanche transient voltage
suppression diodes that are used
here for ESD (Electrostatic Discharge)
Driving the CP2103's /RST pin
low for more than 15 μs will initiate a
CP2103 system reset. The /RST pin is
open drain and reflects the status of
a CP2103 internal power on reset.
The CP2103's V pin is a power
input pin that determines the voltage
level support for the I/O pins.
Voltage at the V pin can vary
between 1.8 volts and V . A 0.1 μF
bypass capacitor is present on the
V pin to suppress noise.
The only remaining components
we need to consider in a CP2103
design are shown in Schematic 3.
Adding these VBUS bypass
capacitors brings the total CP2103
system parts count to seven. It's really
sobering to realize that the seeming
expanse of the schematics is all
contained in the macro view of
the CP2103 and its supporting
components you see in Photo 3.
ExpressPCB pads and traces for the CP2103 hardware
project. Now that we have some idea of what it's going
to take to put a CP2103 USB interface together, I'll come
up with a CP2103/microcontroller hardware design and
have it ready for the next installment of Design Cycle.
We'll also take a closer look at USBXpress and use its
utilities to customize our CP2103. So, polish up your
soldering equipment as you're going to need it.
We're about to add USB to your Design Cycle.
■ Fred Eady can be contacted via email at firstname.lastname@example.org
BUILD IT FEVER
I'm really anxious to lay out the
CP2103; CP2103 Evaluation Kit
EDTP Electronics, Inc.
February 2009 73