DG540 Datasheet, PDF (8/11 Pages) TEMIC Semiconductors – Wideband/Video T Switches

DG540/541/542
Vishay Siliconix
TEST CIRCUITS
+15 V
C
10 W
2.4 V
V+
S₁
D₁
IN_X
S₂
D₂
V_O
R_L
75 W
S₃
S₄
GND
D₃
D₄
V–
R_L
R_L
R_L
C
–15 V
V_OUT
X_TALK(AH) + 20 log_{10 VIN}
FIGURE 6. All Hostile Crosstalk
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_DS(on)]
and capacitance [C_S(on)]. This RC combination has an
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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 W). 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.
Document Number: 70055
S-00399—Rev. G, 13-Sep-99