isl54220 Intersil Corporation, isl54220 Datasheet - Page 7

• Manufacturer Part Number: isl54220
• Description: High-speed Usb 2.0 480mbps Multiplexer
• Manufacturer: Intersil Corporation

Application Block Diagram
Detailed Description
The ISL54220 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 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 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
data signals with minimal distortion.
The ISL54220 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 3.3V supply, these switches have a
nominal r
a r
ON
flatness of 0.94Ω. The r
ON
DD
of 6Ω over the signal range of 0V to 400mV with
to pass USB full speed (12Mbps) differential
VBUS
D-
D+
GND
ON
7
matching between the
D-
D+
SEL
LOGIC CIRCUITRY
ISL54220
VDD
GND
ISL54220
HSD1+
HSD2+
HSD1-
HSD2-
OE
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
switch resistance is nominally 129Ω. See Figures 7, 8, 9, 10
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 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 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
allow to exceed the V
more than -0.3V for normal operation.
However, in the event that the USB 5.25V V
shorted to one or both of the D-/D+ pins, the ISL54220 has
special fault protection circuitry to prevent damage to the
ISL54220 part. The fault circuitry allows the signal pins (D-,
D+, HS1D-, HS1D+, HS2D-, HS2D+) to be driven up to 5.5V
while the V
this condition the part draws < 500µA of current and causes
no stress to the IC. In addition when V
all switches are OFF and the fault voltage is isolated from
ON
switch resistance increases. At signal level of 3.3V, the
DD
supply voltage is in the range of 0V to 5.5V. In
DD
PORTABLE MEDIA DEVICE
DD
voltage rail or go below ground by
µCONTROLLER
TRANSCEIVER
TRANSCEIVER
HIGH_SPEED
FULL-SPEED
FULL-SPEED
HIGH-SPEED
. The signal voltage should not be
USB
USB
OR
OR
DD
is at 0V (ground)
BUS
December 16, 2008
voltage gets
FN6819.0