ISL54208 Datasheet, PDF (9/15 Pages) Intersil Corporation – Low Voltage, Dual SPDT, USB/CVBS/ Audio Switches, with Negative Signal Capability

ISL54208
audio/video playback are intended to be mutually exclusive
operations.
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.
Figures 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 ISL54208. 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.
FIGURE 8. VECTOR-SCOPE PLOT BEFORE SWITCH
FIGURE 9. VECTOR-SCOPE PLOT AFTER SWITCH
Figure 18 shows the differential gain (DG) and differential
phase (DP) plots at the output of the switch using an actual
NTSC composite video signal and a VM700A Video
Measurement Test Set. DG = 0.28% and DP = 0.04deg.
The NC switches are uni-directional switches. The
audio/video sources should be connected at the NC side of
the switch (pins 7 and 8) and the speaker load and video
receiver should be connected at the COM side of the switch
(pins 3 and 4).
The NC switches are active (turned ON) whenever the IN
voltage is ≤ to 0.5V and the CTRL voltage to ≥1.4V.
Note: Whenever the NC switches are ON the USB
transceiver drivers need to be in the high impedance state or
static high or low state.
NO1 and NO2 USB Switches
The two NO (normally open) USB switches (NO1, NO2) are
5Ω bidirectional switches that were designed to pass high-
speed USB differential signals in the range of ±0V to 400mV.
These switches have low capacitance and high bandwidth to
pass USB high-speed signals (480Mbps) with minimum
edge and phase distortion to meet high-speed USB 2.0 high-
speed signal quality specifications. See Figure 14 for High-
speed Eye Pattern taken with switch in the signal path.
The maximum signal range for the USB switches is from
-1.5V to V_DD. The signal voltage at NO1 and NO2 should
not be allow to exceed the V_DD voltage rail or go below
ground by more than -1.5V.
The NO switches are active (turned ON) whenever the IN
voltage is to ≥1.4V.
Note: Whenever the NO switches are ON the audio and
video drivers need to be at ac or dc ground or floating to
keep from interfering with the data transmission.
9
FN6410.0
December 18, 2006