ISL54222_09 Datasheet, PDF (7/15 Pages) Intersil Corporation – High-Speed USB 2.0 (480Mbps) Multiplexer

Application Block Diagram
ISL54222
VBUS
D-
D+
GND
V_DD
ISL54222
SEL
OE
LOGIC CIRCUITRY
HSD1-
D-
HSD1+
D+
GND
HSD2-
HSD2+
µCONTROLLER
USB
HIGH-SPEED
OR
FULL-SPEED
TRANSCEIVER
#1
USB
HIGH_SPEED
OR
FULL-SPEED
TRANSCEIVER
#2
PORTABLE MEDIA DEVICE
Detailed Description
The ISL54222 device is a dual single pole/double throw
(SPDT) analog switch configured as a DPDT that operates
from a single DC power supply in the range of 1.8V to 3.3V.
It was designed to function as a dual 2-to-1 multiplexer to
select between two USB high-speed differential data signals
in portable battery powered products. It is offered in a TDFN,
MSOP, and a small µTQFN packages for use in MP3
players, cameras, PDAs, cellphones, and other personal
media players. The device has an enable pin to open all
switches.
The part consists of four 5.5Ω high speed (HSx) switches.
These switches have high bandwidth and low capacitance to
pass USB high-speed (480Mbps) differential data signals
with minimal edge and phase distortion. They can also swing
from 0V to V_DD to pass USB full speed (12Mbps) differential
data signals with minimal distortion.
The ISL54222 was designed for MP3 players, cameras,
cellphones, and other personal media player applications
that have multiple high-speed or full-speed transceivers
sections and need to multiplex between these USB sources
to a single USB host (computer). A typical application block
diagram of this functionality is previously shown.
A detailed description of the HS switches is provided in the
following section.
High-Speed (HSx) Switches
The HSx switches (HSD1-, HSD1+, HSD2-, HSD2+) are
bi-directional switches that can pass rail-to-rail signals.
When powered with a 1.8V supply, these switches have a
nominal r_ON of 5.5Ω over the signal range of 0V to 400mV
with a r_ON flatness of 0.44Ω. The r_ON matching between the
HSD1 and HSD2 switches over this signal range is only
0.072Ω, ensuring minimal impact by the switches to USB
7
high speed signal transitions. As the signal level increases,
the r_ON switch resistance increases. At signal level of 1.8V,
the switch resistance is nominally 12Ω. See Figures 7, 8, 9,
10, 11, 12 in the “Typical Performance Curves” beginning on
page 9.
The HSx switches were specifically designed to pass USB
2.0 high-speed (480Mbps) differential signals in the range of
0V to 400mV. They have low capacitance (6.5pF) and high
bandwidth to pass the USB high-speed signals with
minimum edge and phase distortion to meet USB 2.0 high
speed signal quality specifications. See Figure 13 in the
“Typical Performance Curves” on page 10 for USB
High-speed Eye Pattern taken with switches in the
differential signal paths.
The HSx switches can also pass USB full-speed signals
(12Mbps) with minimal distortion and meet all the USB
requirements for USB 2.0 full-speed signaling. See Figure 14
and 15 in the “Typical Performance Curves” on page 11 for
USB Full-speed Eye Pattern taken with switches in the
differential signal paths.
The maximum normal operating signal range for the HSx
switches is from 0V to V_DD. The signal voltage should not be
allow to exceed the V_DD voltage rail or go below ground by
more than -0.3V for normal operation.
However, in the event that the USB 5.25V V_BUS voltage gets
shorted to one or both of the D-/D+ pins, the ISL54222 has
special fault protection circuitry to prevent damage to the
ISL54222 part. The fault circuitry allows the signal pins (D-,
D+, HSD1-, HSD1+, HSD2-, HSD2+) to be driven up to 5.5V
while the V_DD supply voltage is in the range of 0V to 3.3V. In
this condition the part draws < 300µA of I_DD current and
causes no stress to the IC. In addition when V_DD is at 0V
(ground) all switches are OFF and the fault voltage is
isolated from the other side of the switch. When V_DD is in the
FN6835.1
May 27, 2009