ISL54416 Datasheet, PDF (9/14 Pages) Intersil Corporation – Low Voltage, Dual SPDT, USB/CVBS/ Audio Switches with Negative Signal Capability

ISL54415, ISL54416, ISL54417
Application Block Diagram
V_BUS
COM1
V_DD
ISL54415
V_TERM
NO1
NO2
D-
USB
FULL-SPEED
D+
TRANSCEIVER
COM2
NC1
NC2
NTSC OR PAL
VIDEO
AUDIO
GND
Detailed Description
The ISL5441X family of devices are dual single pole/double
throw (SPDT) analog switches that operate from a single
power supply. They were designed to function as dual 2 to 1
multiplexers to select between USB differential data signals
and mono Audio/Composite Video Broadcast System
(CVBS). They come in tiny µTQFN package for use in digital
cameras, camcorders, video MP3 players, PDAs,
cellphones, and other personal media players.
All devices in this family consist of two 1Ω normally closed
(NC) Audio/Video switches and two 5Ω normally open (NO)
USB switches. The audio/video switches can accept signals
that swing below ground. They were designed to pass
ground reference audio or DC-restored with synch
composite video signals with minimal distortion. The USB
switches were designed to pass full-speed USB differential
data signals with minimal edge and phase distortion.
The ISL54415 and ISL54416 were specifically designed for
digital cameras, camcorders, MP3 players, cellphones and
other personal media player applications that need to
combine the audio/video jacks and the USB data connector
into a single shared connector, thereby saving space and
component cost. A typical application block diagram of this
functionality is shown above. The ISL54415 and ISL54416
incorporate circuitry for the detection of the USB V_BUS
voltage, which is used to switch between the audio/video
drivers and USB transceiver of media player. The ISL54415
contains additional circuitry to generate the required USB
V_TERM of 3.3V for use with the USB speed setting pull-up
resistor.
The ISL54417 is an audio/video and data switch who’s logic
control is typical of a standard dual SPDT device.
A detailed description of the two types of switches and of
each part type in the ISL5441X family are provided in the
following sections. The digital data transmission (USB, etc.)
9
and audio/video playback are intended to be mutally
exclusive operations.
NC1 and NC2 Audio/Video Switches
The two NC (normally closed) audio/video switches (NC1,
NC2) are 1Ω high bandwidth switches that can pass signals
that swing below ground by as much as 1.5V. They were
design to pass ground reference audio signals and
DC-restored Composite Video Broadcast System (CVBS)
including negative synchronizing pulse with minimal
insertion loss and very low distortion and degradation.
The -3dB bandwidth into 50Ω is 394MHz and into 75Ω is
264MHz. Crosstalk between NC1 and NC2 @ 4MHz is
-60dB which allows composite video to be routed through
one switch and mono-audio through the other switch with
little interference.
The recommended maximum signal range is from -1.5V to
1.5V. You can apply positive signals greater than 1.5V but
the R_ON resistance of the switch increases rapidly above
1.5V. The signal should not be allowed to exceed the V_DD
rail or swing more negative than -1.5V.
Over a signal range of ±1V these switches have an
extremely low R_ON flatness. They can pass a ground
referenced audio signal with very low distortion (<0.007%
THD+N) when delivering 12mW into a 32Ω headphone
speaker load. See Figures 10 and 11 THD+N performance
curves.
Figures 8 and 9 show the vector scope plots of a standard
NTSC color bar signal at both the input (Figure 8) and output
(Figure 9) of the ISL54415. The plots show that except for a
little attentuation, due to switch R_ON and test fixture cabling,
there is virtually no degradation of the video waveform
through the switch.
FN6318.1
June 27, 2006