AN207 View Datasheet(PDF) - Vishay Semiconductors
Part Name
Description
Manufacturer
AN207 Datasheet PDF : 12 Pages
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S
+2 V
VIN
D
300 W
50 W
Test Circuit
AN207
Vishay Siliconix
VOUT
CL = 3 pF
VIN
VOUT
FIGURE 3. Bench Test Switching Times Are Faster Than Data Sheet Limits
As seen in Figure 6, there were significant differences
between the DG271 and the DG611 output wave forms. First,
the DG611 considerably reduced switching glitches. Some
spikes went from 1 V to 0.2 V, a fivefold improvement. Second,
the faster DG611 reduced output delays and produced more
consistent notch widths.
For general purpose switches, it is customary to assume that
all charge injection is due to capacitive coupling from the
output driver into the analog channel. At the low Qinj levels
achieved by the DG61X family, even the spurious capacitance
(due to pin proximity from the logic control pin to the adjacent
drain pin) will contribute a significant amount of charge. For this
reason, it is possible to get minimal glitches by applying the
input signal to the drain pin and using the source pin for the
output.
Document Number: 70605
03-Aug-99
On-Resistance
A low on-resistance switch reduces measurement errors and
helps to achieve fast settling times in test equipment and data
acquisition systems. It is also useful in reducing insertion loss
when switching RF or video signals. The DG611 family
specifies a typical rDS(on) of 18 Ω. This is one of the lowest
values among high-speed analog switches. In order to reduce
parasitic capacitances, the DG611 uses an n-channel
enhancement mode MOSFET for the switch element.
Consequently, its on-resistance increases as the channel
voltage increases. Eventually, as VS approaches V+ the
n-channel MOSFET loses its enhancement voltage (V+) -VS
and turns off.
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