ISL54207 Datasheet, PDF (8/14 Pages) Intersil Corporation – Low Voltage, Dual SPDT, USB/CVBS/ Audio Switches, with Negative Signal Capability

ISL54207
Application Block Diagram
VBUS
22kΩ
COM1
VDD
ISL54207
LOGIC CIRCUITRY
4MΩ
4MΩ
CTRL
NO1
NO2
COM2
50kΩ
NC1
NC2
50kΩ
GND
mCONTROLLER
D-
USB
HIGH-SPEED
D+
TRANSCEIVER
NTSC or PAL
VIDEO
AUDIO
Detailed Description
The ISL54207 device is a dual single pole/double throw
(SPDT) analog switch device that operates from a single DC
power supply in the range of 2.7V to 3.6V. It was designed to
function as a dual 2 to 1 multiplexer to select between USB
differential data signals and mono audio/composite video
baseband signals (CVBS). It comes in tiny μTQFN and
TDFN packages for use in cameras, camcorders, video MP3
players, PDAs, cell phones, and other personal media
players.
The part consists of two 3Ω audio/video switches and two
5Ω 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 high-speed USB differential
data signals with minimal edge and phase distortion.
The ISL54207 was specifically designed for digital cameras,
camcorders, MP3 players, cell phones 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 ISL54207 incorporates circuitry for the detection of the
USB V_BUS voltage, which is used to switch between the
audio/video drivers and USB transceiver of the media player.
The ISL54207 contains a logic control pin (CTRL) that when
driven Low while VBUS is Low, opens all switches and puts
the part into a low power state, drawing typically 1nA of I_DD
current.
A detailed description of the two types of switches is
provided in the following sections. The USB transmission
and audio/video playback are intended to be mutually
exclusive operations.
8
NC1 and NC2 Audio/Video Switches
The two NC (normally closed) audio/video switches (NC1,
NC2) are 3Ω switches that can pass signals that swing
below ground by as much as 1.5V. They were designed to
pass ground reference audio signals and DC restored
composite base-band signals (CVBS), including negative
synchronizing pulse with minimal insertion loss and very low
distortion and degradation.
The -3dB bandwidth into 75Ω is 338MHz (Figure 17).
Crosstalk between NC1 and NC2 @ 4MHz is -78dB
(Figure 16), 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 (0.707Vrms) with V_DD > 2.7V,
these switches have an extremely low r_ON resistance
variation. They can pass a ground referenced audio signal
with very low distortion (<0.06% THD+N) when delivering
15.6mW into a 32Ω headphone speaker load. See
Figures 10, 11, 12, and 13 THD+N performance curves.
Figure 8 and 9 shows the vector scope plots of a standard
NTSC color bar signal at both the input (Figure 8) and output
(Figure 9) of the ISL54207. The plots show that except for a
little attenuation due to switch r_ON and test fixture cabling,
there is virtually no degradation of the video waveform
through the switch.
FN6403.0
December 5, 2006