AN207 Vishay Intertechnology, AN207 Datasheet - Page 5

• Manufacturer Part Number: AN207
• Description: 15-ns DG611 Switch Family Combines Benefits of CMOS And Dmos
• Manufacturer: Vishay Intertechnology

Figure 7 illustrates typical on-resistance curves. Curve (a)
represents single 5-V operation. Assuming a maximum
acceptable r
range goes from 0 V to slightly over 2 V. Curve (b) shows
operation with V+ = 12 V. Now the usable signal range has
increased to 8 V. If you want to operate in the flat,
low-resistance part of the curve, you may want to limit your
analog signal to no more than 6 V. Curve (c) was generated
using a –10-mA I
shows an r
to 7.2 V, and this creates a partial channel enhancement.
ESDS (ESD Sensitivity)
By incorporating a CMOS driver in front of the DMOS FET,
direct access to the DMOS gate has been eliminated. By itself,
this goes a long way to reduce ESD sensitivity. Additional ESD
protection diodes have been added to the source and drain
pins. Nevertheless, to maintain high speed, a compromise
between
on-capacitance had to be reached. This means that the
protection diodes are relatively small and protect only up to
about 500 V. To prevent damage from high-energy
electrostatic fields, anti-static handling precautions must be
observed at all times.
Applications
Following is a collection of practical application hints and
design ideas intended to help you design with the DG61X
family.
Document Number: 70605
03-Aug-99
600
500
400
300
200
100
0
0
FIGURE 7. Typical r
DS(on)
ESD
DS(on)
a)
2
= 480
D
protection,
4
value of 200
current. Note that when V
6
V
. To sink 10 mA, V
S
– Source Voltage (V)
b)
8
DS(on)
speed,
10
a) V+ = 5 V
b) V+ = 12 V
c) V+ = 12 V, I
, the usable analog signal
Characteristics
c)
12
on-resistance, and
V
S
14
D
SD
+5 V
has gone down
GND
S
V
= 10 mA
L
= 12 V, it still
16
V–
V+
18
I
SD
20
High-Speed 8-Channel Analog Multiplexer
If you are designing a high-speed data acquisition system,
then you will need a very fast analog multiplexer. A fast
multiplexer like the DG408 specifies a typical transition time of
160 ns. By using the DG611 to make the multiplexer shown in
Figure 9, you will achieve transition times in the 30-ns range,
a sixfold speed improvement. This added speed will allow you
to achieve sampling rates in excess of 3 MHz, as
demonstrated below.
For an 8-channel multiplexer the maximum sampling rate is
given by:
for an accuracy of 0.01% (12 bits) N = 9.
For small signals, let us assume that typical r
The output node capacitance is given by:
C
where t
(on)
= 1 C
FIGURE 8. ESD Protection Diodes are Located at all
f
S
SETTLING
IN
D(on)
8
V–
V+
+ 7 C
(t
= N
Control and Switch Pins
SETTLING
D(off)
r
1
DS(on)
= 10 pF + 7
www.vishay.com FaxBack 408-970-5600
S
t
TRANS
C
(on)
Vishay Siliconix
)
2 pF = 24 pF
V–
V+
DS(on)
AN207
D
= 18
(1)
(2)
6-5