ISL54225_10 Datasheet, PDF (9/18 Pages) Intersil Corporation – High-Speed USB 2.0 (480Mbps) Multiplexer with Overvoltage Protection (OVP)

ISL54225
Application Block Diagram
VBUS
D-
D+
GND
500Ω
ISL54225
VDD
VDD
SEL
4MΩ
OE
LOGIC CIRCUITRY
4MΩ
HSD1-
D-
HSD1+
OVP
D+
HSD2-
HSD2+
GND
µCONTROLLER
USB
HIGH-SPEED
OR
FULL-SPEED
TRANSCEIVER
#1
USB
HIGH_SPEED
OR
FULL-SPEED
TRANSCEIVER
#2
PORTABLE MEDIA DEVICE
Detailed Description
The ISL54225 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
5.25V.
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, 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 and put the part in a low power state.
The part contains special overvoltage detection and
protection (OVP) circuitry on the D-/D+ COM pins. This
circuitry acts to open the USB in-line switches when the
part senses a voltage on the COM pins that is >3.8V
(typ) or < -0.5V (typ). It isolates voltages up to 5.25V
and down to -5V from getting through to the other side
of the switch to protect the USB transceivers connected
at the signal pins (HSD1-, HSD1+, HSD2-, HSD2+).
The part consists of four 6.5Ω 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 3.6V to pass USB full speed (12Mbps)
differential data signals with minimal distortion.
The ISL54225 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) Data Switches
The HSx switches (HSD1-, HSD1+, HSD2-, HSD2+) are
bi-directional switches that can pass USB high-speed and
USB full-speed signals when V_DD is in the range of 2.7V
to 5.25V.
When powered with a 2.7V supply, these switches have a
nominal r_ON of 6.5Ω over the signal range of 0V to
400mV with a r_ON flatness of 0.3Ω. The r_ON matching
between the HSD1x switches and HSD2x switches over
this signal range is only 0.2Ω, 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 12Ω. See Figures 9, 10, 11, 12, 13, 14, 15 and
16 in the “Typical Performance Curves” beginning on
page 12.
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 21 in the “Typical Performance Curves” on
page 14 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 22 in the “Typical Performance Curves” on
page 14 for USB Full-speed Eye Pattern taken with
switch in the signal path.
9
FN7627.0
July 2, 2010