Datasheet

© 2006 Fairchild Semiconductor Corporation www.fairchildsemi.com
FSA201 Rev. 1.2.2 3
FSA201

 USB2.0 Full-Speed and Audio Switches with Negative Signal Capability
Functional Description
The FSA201 is a combined USB and audio switch that
enables sharing the D+/D- lines of a USB connector with
stereo audio CODEC outputs. The switch is optimized
for full-speed USB signals and includes an automatic
V
BUS
-detection circuit. When a USB connector, rather
than a headphone, is connected to the ultra-portable
device the switch is automatically configured for full-
speed USB data transfer. If no V
BUS
is detected, and yet
V
AUDIO
is present, the switch is configured for the low-
distortion audio switch path. The audio switch path also
handles negative signals (down to -2V), which
eliminates the need for large coupling capacitors.
For those applications where the V
BUS
is generated as a
self-powered device or where V
BUS
is not removed, the
A
SEL
pin provides the ability to switch, under software
control, to the audio path. The A
SEL
pin is internally
terminated by a resistor to GND (typical value 3M) and
requires no connection for the standard ultra-portable
(cell-phone, MP3, or Portable Media Player). In an
application where the supply to the FSA201 V
BUS
pin is
not guaranteed to be removed, a GPIO pin can be used
to switch out of full-speed USB mode into audio mode,
using the A
SEL
pin.
The FSA201 V
BUS
pin must be connected directly to
V
BUS
or a supply > 3.8V, not an LDO regulated down to
3.6V or a V
bat
-generated supply that may fall below 3.8V
in normal operation (see the Application Diagram).
Application Diagram
V
bus
V
audio
Switch Select
Control Circuitry
D+/R
D-/L
D+
R
D-
L
A
Sel
R
pd
GND
GND
5V
Audio
CODEC
FS-USB
Source
3.0V - 3.6V
USB
Mini-AB
Connecto
r
V
bus
ID
Figure 4. Application Diagram