ISL54222A_10 Datasheet, PDF (9/19 Pages) Intersil Corporation – High-Speed USB 2.0 (480Mbps) Multiplexer

ISL54222A
Application Block Diagram
V_BUS
D-
D+
GND
V_DD
ISL54222A
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 ISL54222A 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 MSOP, TDFN and small µTQFN packages for use in MP3
players, cameras, PDAs, cell phones, and other personal
media players.
The part consists of four 4.4Ω 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 3.3V to pass
USB full speed (12Mbps) differential data signals with
minimal distortion.
The device has an enable pin to open all switches and put
the part in a low power down state. It can be used to
facilitate proper bus disconnect and connection when
switching between the USB sources.
The ISL54222A was designed for MP3 players, cameras,
cell phones, 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 shown
on page 9.
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 0V to 3.3V signals.
When powered with a 1.8V supply, these switches have a
nominal r_ON of 5.7Ω over the signal range of 0V to 400mV
with a r_ON flatness of 0.60Ω. 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
high-speed signal transitions. As the signal level increases,
the r_ON switch resistance increases. With supply of 1.8V,
the switch resistance with the signal level at the rail is
nominally 12Ω. See Figures 7, 8, 9, 10, 11 and 12 in the
“Typical Performance Curves” beginning on page 11.
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 (4.2pF) 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 12 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
Figures 14 and 15 in the “Typical Performance Curves”
on page 13 for USB Full-speed Eye Patterns taken with
switches in the differential signal paths.
The maximum normal operating signal range for the
HSx switches is from 0V to 3.3V. The signal voltage
should not be allowed to exceed 3.3V 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
ISL54222A has special fault protection circuitry to
prevent damage to the ISL54222A 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
9
FN6902.1
February 4, 2010