SGM7222 Datasheet, PDF (9/16 Pages) SG Micro Corp – DPDT Analog Switch

SGM7222
APPLICATION NOTES
High Speed USB 2.0
(480Mbps) DPDT Analog Switch
Meeting USB 2.0 V_BUS Short Requirements
In section 7.1.1 of the USB 2.0 specification, it notes that
USB devices must be able to withstand a V_BUS short to
D+ or D- when the USB devices is either powered off or
powered on The SGM7222 can be successfully
configured to meet both these requirements.
Power-Off Protection
For a V_BUS short circuit the switch is expected to
withstand such a condition for at least 24 hours. The
SGM7222 has specially designed circuitry which
prevents unintended signal bleed through as well as
guaranteed system reliability during a power-down,
over-voltage condition. The protection has been added to
the common pins (D+, D-).
Power-On Protection
The USB 2.0 specification also notes that the USB device
should be capable of withstanding a V_BUS short during
transmission of data. This modification works by limiting
current flow back into the V+ rail during the over-voltage
event so current remains within the safe operating range.
In this application, the switch passes the full 5.25V input
signal through to the selected output, while maintaining
specified off isolation on the un-selected pins.
SG Micro Corp
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