FSA3200 Datasheet, PDF (2/13 Pages) Fairchild Semiconductor – Two-Port, High-Speed USB2.0 Switch with Mobile High-Definition Link (MHL™)

Switch Power Operation
In normal operation, the FSA3200 is powered from the
V_CC pin, which typically is derived from a regulated
power management device. In special circumstances,
such as production test or system firmware upgrade, the
device can be powered from the V_BUS pin. In this mode
of operation, a valid V_BUS voltage is present (per USB2.0
specification) and V_CC=0 V, typically due to a no-battery
condition. With the SELn pins strapped LOW (via
external resistor), the FSA3200 closes the USB path,
enabling the initial programming of the system directly
from the USB connector. Once the system has normal
operating supply power with V_CC present, the V_BUS
supply is not utilized and normal switch operation
commences. Optionally, the Power Select Override
(PSO) pin can be set HIGH to force the device to be
powered from V_BUS.
The V_BUS / V_CC detection capability is not intended to be
an accurate determination of the voltages present,
rather a state condition detection to determine which
supply should be used. These state determinations rely
on the voltage conditions as described in the Electrical
Characterization tables below.
V_BUS
V_CC
PSO
Switch
Power
Selection
Charge Pump
& Regulator
Switch
Power
Source
Switch
Power
Figure 2. Simplified Logic of Switch Power Selection Circuit
Table 1. Switch Power Selection Truth Table
V_CC
V_BUS
PSO⁽¹⁾
Switch Power Source
0
0
0
No switch power, switch paths high-Z
0
1
0
V_BUS
1
0
0
V_CC
1
1
0
V_CC
0
0
1
No switch power, switch paths high-Z
0
1
1
V_BUS
1
0
1
V_CC(2)
1
1
1
V_BUS
Notes:
1. Control inputs should never be left floating or unconnected. If the PSO function is used, a weak pull-up resistor
(3 MΩ) should be used to minimize static current draw. If the PSO function is not used, tie directly to GND.
2. PSO control is overridden with no V_BUS and the power selection is switched to V_CC.
Table 2. Data Switch Select Truth Table
SEL1⁽³⁾
SEL2⁽³⁾
Function
0
0
D+/D- connected to USB+/USB-, ID_CO connected to ID_USB
0
1
D+/D- connected to USB+/USB-, ID_COM connected to ID_MDV
1
0
D+/D- connected to MDV+/MDV-, ID_COM connected to ID_USB
1
1
D+/D- connected to MDV+/MDV-, ID_COM connected to ID_MDV
Note:
3. Control inputs should never be left floating or unconnected. To guarantee default switch closure to the USB
position, the SEL pins should be tied to GND with a weak pull- down resistor (3 MΩ) to minimize static current draw.
© 2010 Fairchild Semiconductor Corporation
FSA3200 • Rev. 1.0.8
2
www.fairchildsemi.com