ISL54224 Datasheet, PDF (9/18 Pages) Intersil Corporation – High-Speed USB 2.0 (480Mbps) Multiplexer with Overvoltage Protection (OVP) and Overvoltage Indicator Output

ISL54224
Application Block Diagram
VBUS
D-
D+
GND
3.3V
500Ω
3.3V
ISL54224
VDD
SEL
LOGIC CIRCUITRY
4MΩ
OE/ALM
4MΩ
HSD1-
D-
HSD1+
100kΩ
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 ISL54224 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 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 device has an open drain OE/ALM pin that can be
driven “Low” to open all switches. The OE/ALM pin gets
internally pulled “Low” whenever the part senses an
overvoltage condition. The pin must be externally pulled
“High” with a 100kΩ pull-up resistor and monitored for a
“Low” to determine when an overvoltage condition has
occurred.
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 ISL54224 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 a 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 20 in
the “Typical Performance Curves” on page 14 for USB
High-speed Eye Pattern taken with switch in the signal
path.
9
FN6969.0
June 7, 2010