ISL54228 Datasheet, PDF (9/17 Pages) Intersil Corporation – High-Speed USB 2.0 (480Mbps) DPST Switch with Overvoltage Protection (OVP)

ISL54228
Application Block Diagram
3.3V
500Ω
VDD
VBUS
D-
D+
GND
COM -
OVP
DET
COM +
ISL54228
Logic
Control
4MΩ
LP
OE
4MΩ
D-
D+
GND
µCONTROLLER
USB
HIGH-SPEED
OR
FULL-SPEED
TRANSCEIVER
PORTABLE MEDIA DEVICE
Detailed Description
The ISL54228 device is a dual single pole/single throw
(SPST) analog switch configured as a DPST that
operates from a single DC power supply in the range of
2.7V to 5.25V.
It was designed for switching a USB high-speed source
or full-speed source in portable battery powered
products. It is offered in small µTQFN and TDFN
packages for use in MP3 players, cameras, PDAs,
cellphones, and other personal media players.
The part consists of two 3.5Ω high speed SPST
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 device has a single logic control pin (OE) to open
and close the two SPST switches. The part has an LP
control pin to put the part in a low power state.
The part contains special overvoltage protection (OVP)
circuitry on the COM+ and COM- pins. This circuitry
acts to open the SPST switches when the part senses a
voltage on the COM pins that is >3.8V (typ) or
< -0.45V (typ). It isolates voltages up to 5.25V and
down to -5V from getting through to the other side of
the switches (D-, D+) to protect the USB down-stream
transceiver connected at the D+ and D- pins.
The ISL54228 was designed for MP3 players, cameras,
cellphones, and other personal media player
9
applications that need to switch a high-speed or full-
speed transceiver source. A typical application block
diagram of this functionality is previously shown.
A detailed description of the SPST switches is provided
in the following section.
High-Speed (Dx) SPST Switches
The Dx switches are bi-directional switches that can
pass USB high-speed and USB full-speed signals when
VDD 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 3.5Ω over the signal range of 0V to
400mV with a r_ON flatness of 0.26Ω. The r_ON matching
between the 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
9.8Ω. See Figures 8, 9, 10, 11, 12, 13 in the “Typical
Performance Curves” beginning on page 12.
The Dx 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 14 in the “Typical Performance Curves” on
page 13 for USB High-speed Eye Pattern taken with
switch in the signal path.
The Dx switches can also pass USB full-speed signals
(12Mbps) in the range of 0V to 3.6V with minimal
FN7628.0
July 29, 2010