© 2010 Fairchild Semiconductor Corporation

www.fairchildsemi.com

FSA801 • Rev. 1.0.3

3

Mode Descriptions

The FSA801 has three select pins to control the

switching operations, SEL[0], SEL[1], and SEL[2]

described in Table 1.

Table 1.

Selection Truth Table

SEL[2]

SEL[1]

SEL[0]

Switch Action

Description

0

0

0

OPEN

Open all switch paths (device in low-power mode)

0

0

1

USB1, UART

Closes USB1 path to D+/D-, default condition

(1)

- DP_CON connected to DP_HOST1

- DM_CON connected to DM_HOST1

0

1

0

USB2, UART

Closes USB2 path to D+/D-

- DP_CON connected to DP_HOST2

- DM_CON connected to DM_HOST2

0

1

1

AUDIO

Closes audio path to D+/D- only, no microphone

switched

- DP_CON connected to R_HOST

- DM_CON connected to L_HOST

1

0

0

MONO AUDIO with MIC

on D+

(2)

Closes audio path to DM_CON and microphone on

DP_CON pin. This is a mono-audio application.

- DP_CON connected to MIC

- DM_CON connected to L_HOST

1

0

1

STEREO AUDIO with MIC

on VBUS

(2)

pin. This mode is typically used for stereo headset

with microphone.

- DP_CON connected to R_HOST

- DM_CON connected to L_HOST

1

1

0

Undefined

Reserved; do not use.

1

1

1

Charger Detection Reset

Charger Detection Reset. Selecting this mode for

greater than 30 µs resets the FSA801 to check for a

charger, the next time a SEL[2:0] state of ‘000’ is

applied for more than 30 µs.

Notes:

1.

The SELECT pins are CMOS inputs and should not be left in a floating condition. Some applications require the

UART path be in the CLOSED position on power-up for initial programming of the device under test. If that

condition is desired, the three SELECT pins should be pulled to the correct levels with external resistors that

should exceed 100 K

Ω to reduce the static power consumption. In other applications, adding weak pull-down

resistors to GND defaults the device to all paths open (low-power mode).

2.

When the audio switch is in the OPEN position, the R and L are terminated to GND with internal termination

resistors to discharge any stray capacitance that could cause audio pop.