DG540 TEMICs, DG540 Datasheet - Page 8

• Manufacturer Part Number: DG540
• Description: Wideband/Video T Switches
• Manufacturer: TEMICs

Test Circuits (Cont’d)
Applications
Device Description
The DG540/541/542 family of wideband switches offers
true bidirectional switching of high frequency analog or
digital signals with minimum signal crosstalk, low insertion
loss, and negligible non-linearity distortion and group
delay.
Built on the Siliconix D/CMOS process, these “T” switches
provide excellent off-isolation with a bandwidth of around
500 MHz (350 MHz for DG541). Silicon-gate D/CMOS
processing also yields fast switching speeds.
An on-chip regulator circuit maintains TTL input
compatibility over the whole operating supply voltage
range, easing control logic interfacing.
Circuit layout is facilitated by the interchangeability of
source and drain terminals.
Frequency Response
A single switch on-channel exhibits both resistance
[r
DG540/541/542
8
DS(on)
] and capacitance [C
10
S(on)
2.4 V
]. This RC combination has
X
TALK(AH)
S
IN
S
S
S
1
2
3
4
+15 V
GND
X
Figure 6. All Hostile Crosstalk
V+
20 log
–15 V
V–
10
C
D
D
D
D
V
1
2
3
4
C
V
OUT
IN
an attenuation effect on the analog signal – which is
frequency dependent (like an RC low-pass filter). The
–3-dB bandwidth of the DG540 is typically 500 MHz (into
50
the switch channel can not be represented by a two stage RC
combination. The on capacitance of the channel is
distributed along the on-resistance, and hence becomes a
more complex multi stage network of R’s and C’s making
up the total r
for more details.
Off-Isolation and Crosstalk
Off-isolation and crosstalk are affected by the load
resistance and parasitic inter-electrode capacitances.
Higher off-isolation is achieved with lower values of R
However, low values of R
gain adjustments down the line. Stray capacitances, even a
fraction of 1 pF, can cause a large crosstalk increase. Good
layout and ground shielding techniques can considerably
improve your ac circuit performance.
R
L
This measured figure of 500 MHz illustrates that
R
L
DS(on)
R
L
75
and C
R
L
S-53694—Rev. E, 28-May-97
S(on)
L
increase insertion loss requiring
. See Application Note AN502
V
O
Siliconix
L
.