V
GATE
∆V
(a)
TOP: 5 V/div
BOT: 50 mV/div
HOR: 0.5 µs/div
POINT (1)
(b)
TOP: 5 V/div
BOT: 50 mV/div
HOR: 0.5 µs/div
POINT (2)
Figure 10. Waveforms for Points (1) and (2) of Figure 9
capacitances to the signal of an adjacent channel
can form ghosts and signal interference. To
help obtain high degrees of isolation, it becomes
necessary to exercise careful circuit layout,
reducing parasitic capacitive and inductive
couplings, and to use proper shielding and
bypassing techniques. Figure 11 shows the
excellent
off-isolation
and
crosstalk
performance typical of this family of DMOS
analog switches.
Insertion Loss
At low frequencies, the attenuation caused by
the switch is a function of its on-resistance and
the load impedance. They form a simple series
voltage divider network. As an example, for a
600
Ω
load impedance the insertion loss for
voice signals (1 V
rms
at 3 kHz) is less than 0.3
dB. Thus, the SD5000 series make good audio
crosspoint switches.
1 V
rms
160
600 Ω
600
Ω
600
Ω
600
Ω
140
120
Crosstalk
Crosstalk
(dB)
100
80
Off Isolation
1 V
rms
600 Ω
600
Ω
60
40
1k
Off Isolation
10 k
100 k
1M
10 M 100 M
Frequency (Hz)
Figure 11. SD5000 Crosstalk and Off Isolation vs Frequency
6
Linear Integrated Systems, Inc.
●
4042 Clipper Ct.
●
Fremont, CA 94538
●
Tel: 510 490-9160
●
Fax: 510 353-0261
LINEAR [ LINEAR INTEGRATED SYSTEMS ]
