DG540_11 Datasheet, PDF (8/18 Pages) Vishay Siliconix – Wideband/Video 'T' Switches

DG540, DG541, DG542
Vishay Siliconix
TEST CIRCUITS
+ 15 V
C
10 Ω
2.4 V
V+
S₁
D₁
IN_X
S₂
D₂
V_O
R_L
75 Ω
S₃
S₄
GND
D₃
D₄
V-
R_L
R_L
R_L
C
- 15 V
V_OUT
X_{TA LK(AH)} = 20 log_{10 VIN}
Figure 6. All Hostile Crosstalk
APPLICATIONS
Device Description
Frequency Response
The DG540, DG541, DG542 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.
A single switch on-channel exhibits both resistance (R_DS(on))
and capacitance (C_S(on)). This RC combination has 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 ). This measured
figure of 500 MHz illustrates that 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_DS(on) and
C_S(on). See Application Note AN502 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_L. However,
low values of R_L increase insertion loss requiring 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.
www.vishay.com
Document Number: 70055
8
S11-1429–Rev. H, 18-Jul-11
This document is subject to change without notice.
THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000