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FSA321 — USB2.0 Hi-Speed (480Mbps) and
Audio Switches with Negative Signal Capability and
Built-in Termination on Unselected Audio Paths
Features
Description
The FSA321 is a Double-Pole, Double Throw (DPDT)
multiplexer that combines a low-distortion audio and a
USB2.0 High-Speed (HS) switch path. This configuration
enables audio and USB data to share a common
connector port. The architecture is designed to allow
audio signals to swing below ground. This means a
common USB and headphone jack can be used for
personal media players and portable peripheral devices.
Audio: 1.8 Typical On Resistance
HS-USB: 8 Typical On Resistance
HS-USB: 5pF Typical On Capacitance
USB Path -3db Bandwidth: > 720MHz
Negative Swing Capable Audio Channel
Power-off Protection on Common D+/R, D-/L Ports
Automatic USB Detection (Configurable)
OVT on all I/O Ports
Flow-Through Pin Out Eliminates PCB Vias
Built-In Termination on Unselected Audio Paths
to Inhibit Audio Pop
Applications
Since USB2.0 is an industry standard for shared datapath in portable devices, FSA321 can be configured for
automatic VBUS detection. The FSA321 includes a
power-off feature as well as over-voltage tolerance to
minimize current consumption when VSW exceeds VCC.
Typical applications involve switching in portables and
consumer applications, such as cell phones, digital
cameras, and notebooks with hubs or controllers.
.
MP3, Cell Phone, PDA, Digital Camera, and
Notebook
LCD Monitor, TV, and Set-Top Box
Ordering Information
Part Number
Package
Number
Top Mark
Package Description
FSA321UMX
MLP010A
GL
10-Lead Quad, Ultrathin Molded Leadless Package (MLP), 1.4 x 1.8mm
Figure 1. Analog Symbol
© 2007 Fairchild Semiconductor Corporation
FSA321 • Rev 1.0.6
www.fairchildsemi.com
FSA321 — USB2.0 Hi-Speed and Audio Switches with Negative Signal Capability
March 2013
L
3
GND
4
A/LP Sel
5
R
D-
2
1
6
7
10
D+
9
V CC
8
USB Sel
D-/L D+/R
Figure 2. UMLP
Pin Definitions
Pin #
Name
9
VCC
Description
Power supply
5
A/LP Sel
Audio Select Override and Power-Save Mode. This pin can be used to override USB Sel for
applications where analog audio is transmitted on the USB D+, D- lines. This same select pin is
used to put the FSA321 in low-power mode when USB Sel is LOW, not transmitting audio signals
or USB data. The FSA321 has a weak internal pull-down, setting its default state to LOW and
allowing this pin to float when not in use.
8
USB Sel
USB Path select pin. Can be connected to USB connector VBUS pin for automatic USB detection.
10, 1
D+, D-
2, 3
R, L
7, 6
USB data bus input sources
Audio right and left input sources
D+/R, D-/L USB and audio common connector ports
Truth Table
VCC
USB Sel(1)
A/LP Sel
LOW
(2)
(2)
Audio Mode
USB Mode
Remarks
OFF
OFF
Disabled Inputs High-Z
HIGH
HIGH
LOW
OFF
ON
USB Communication
HIGH(2)
HIGH(2)
HIGH(2)
ON
OFF
Audio Override on USB
HIGH(2)
LOW
HIGH(2)
OFF
OFF
Low Power Mode
(2)
LOW
LOW
ON
OFF
Audio Out
HIGH
Notes:
1. Forcing USB Sel HIGH when VBUS is present allows for automatic USB detection.
2. HIGH is the threshold as defined to meet USB2.0 VCC requirements and audio supply threshold in a system
(see DC Tables).
© 2007 Fairchild Semiconductor Corporation
FSA321 • Rev.1.0.6
www.fairchildsemi.com
2
FSA321 — USB2.0 Hi-Speed and Audio Switches with Negative Signal Capability
Pin Configuration
The FSA321 is a combined USB and audio switch that
enables sharing the D+/D- lines of a USB connector with
stereo audio CODEC outputs. The USB Sel pin has an
internal pull-down resistor that results in a default audiomode configuration. The switch can be configured for
auto USB detection by connecting the VBUS pin to the
USB Sel pin. The audio switch path also handles
negative signals, eliminating the need for large coupling
capacitors and greatly reducing the potential for audio
pop. Termination resistors on the audio R and L ports
are enabled when the switch is in USB mode, this also
helps reduce audio pop when enabling the audio path.
The FSA321 allows for an audio override state by
forcing A/LP Sel high when USB Sel is high. This is
useful for USB car kit applications or if the device is in a
cradle charger when “Send/End” is pressed.
Application Diagram
VCC
0.1µF
USB 2.0
Hi-Speed
Controller
D+
USB Sel
D+/R
FSA321
R
Audio
CODEC
D-/L
Shared USB and Audio
Connector
D-
L
Figure 3. Typical Application Diagram
© 2007 Fairchild Semiconductor Corporation
FSA321 • Rev.1.0.6
www.fairchildsemi.com
3
FSA321 — USB2.0 Hi-Speed and Audio Switches with Negative Signal Capability
Functional Description
Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be
operable above the recommended operating conditions and stressing the parts to these levels is not recommended.
In addition, extended exposure to stresses above the recommended operating conditions may affect device reliability.
The absolute maximum ratings are stress ratings only.
Symbol
VCC
Parameter
Min.
Max.
Unit
Supply Voltage
-0.5
4.6
V
USB Sel
USB Select Control Signal
-0.5
6.0
V
A/LP Sel
Power Save Mode Control Signal
-0.5
6.0
V
USB Path Active
-1.0
4.6
Audio Path Active
VCC-4.6V
4.6
-0.50
5.25
Switch I/O Voltage(3)
VSW
DC Switch I/O Voltage
IIK
USB Path Active
(3)
Audio Path Active
Input Clamp Diode Current
ISW
Switch I/O Current (Continuous)
ISWPEAK
Peak Switch Current (Pulsed at
1ms Duration,