ISL54221 Datasheet, PDF (7/13 Pages) Intersil Corporation – High-Speed USB 2.0 (480Mbps) Multiplexer

Application Block Diagram
ISL54221
VBUS
D-
D+
GND
V_DD
ISL54221
SEL
OE
LOGIC CIRCUITRY
HSD1-
D-
HSD1+
D+
GND
HSD2-
HSD2+
µCONTROLLER
USB
HIGH-SPEED
OR
FULL-SPEED
TRANSCEIVER
USB
HIGH_SPEED
OR
FULL-SPEED
TRANSCEIVER
PORTABLE MEDIA DEVICE
Detailed Description
The ISL54221 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 2.7V to 5.5V.
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 small
µTQFN package 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 6Ω 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 ISL54221 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 shown on page 7.
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 3.3V supply, these switches have a
nominal r_ON of 6Ω over the signal range of 0V to 400mV with
a r_ON flatness of 0.94Ω. The r_ON matching between the
7
HSD1 and HSD2 switches over this signal range is only
0.12Ω, ensuring minimal impact by the switches to USB
high-speed signal transitions. As the signal level increases,
the r_ON switch resistance increases. At signal level of 3.3V,
the switch resistance is nominally 129Ω. See Figures 7, 8, 9
and 10 in the “Typical Performance Curves” 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 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 11 in the
“Typical Performance Curves” on page 10 for USB
High-speed Eye Pattern taken with switch in the signal path.
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 12
in the “Typical Performance Curves” on page 11 for the USB
Full-speed Eye Pattern taken with switch in the signal path.
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 ISL54221 has
special fault protection circuitry to prevent damage to the
ISL54221 part. The fault circuitry allows the signal pins (D-,
D+, HS1D-, HS1D+, HS2D-, HS2D+) to be driven up to 5.5V
while the V_DD supply voltage is in the range of 0V to 5.5V. In
this condition the part draws < 500µA of current and causes
no stress to the IC. In addition when V_DD is at 0V (ground)
FN6820.0
December 16, 2008