AD204KN View Datasheet(PDF) - Analog Devices
Part Name
Description
Manufacturer
AD204KN Datasheet PDF : 12 Pages
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AD202/AD204
AD246 Clock Driver. The AD246 is a compact, inexpensive
clock driver that can be used to obtain the required clock from a
single 15 V supply. Alternatively, the circuit shown in Figure 4
(essentially an AD246) can be used. In either case, one clock
circuit can operate at least 32 AD204s at the rated minimum
supply voltage of 14.25 V and one additional isolator can be
operated for each 40 mV increase in supply voltage up to 15 V.
A supply bypass capacitor is included in the AD246, but if many
AD204s are operated from a single AD246, an external bypass
capacitor should be used with a value of at least 1 mF for every
five isolators used. Place the capacitor as close as possible to the
clock driver.
14 6 5
6
180pF
1C
3
RC
2
R
49.9k⍀
CD
4047B
TELEDYNE 1N914
TSC426
10 2
7
Q
4
5
12 9 8 7 4
1N914
3
15V
CLK
OUT
+ 1F
35V
CLK AND
PWR COM
Figure 4. Clock Driver
Input Configurations. The AD202 and AD204 have been
designed to be very easy to use in a wide range of applications.
The basic connection for standard unity gain applications, useful
for signals up to ± 5 V, is shown in Figure 5; some of the possible
variations are described below. When smaller signals must be
handled, Figure 6 shows how to achieve gain while preserving a
very high input resistance. The value of feedback resistor RF
should be kept above 20 kW for best results. Whenever a gain of
more than five is taken, a 100 pF capacitor from FB to IN COM
is required. At lower gains this capacitor is unnecessary, but it
will not adversely affect performance if used.
2k⍀
(SEE TEXT)
VSIG
(؎5V)
FB
IN–
IN+
IN COM
OUT
HI
OUT
LO
AD202
OR
AD204
VOUT
؎5V
15V OR
CLOCK
100pF
RF
2k⍀
VSIG
RG
AD202
OR
AD204
VO
( ) VO = V SIG ؋ 1 + –RR–GF–
RF 20k⍀
Figure 6. Input Connections for Gain > 1
The noninverting circuit of Figures 5 and 6 can also be used to
your advantage when a signal inversion is needed: just interchange
either the input leads or the output leads to get inversion. This
approach retains the high input resistance of the noninverting
circuit, and at unity gain no gain-setting resistors are needed.
When the isolator is not powered, a negative input voltage of
more than about 2 V will cause an input current to flow. If the
signal source can supply more than a few mA under such con-
ditions, the 2 kW resistor shown in series with IN+ should be
used to limit current to a safe value. This is particularly impor-
tant with the AD202, which may not start if a large input current
is present.
Figure 7 shows how to accommodate current inputs or sum
currents or voltages. This circuit can also be used when the
input signal is larger than the ± 5 V input range of the isolator;
for example, a ± 50 V input span can be accommodated with
RF = 20 kW and RS = 200 kW. Once again, a capacitor from FB
to IN COM is required for gains above five.
IS
RS2
RF
VS2
RS1
VS1
AD202
OR
AD204
V
( ) V = – VS1 –RR–SF–1 + V S2 –RR–SF–2 + IS RF + ...
RF 20k⍀
Figure 7. Connections for Summing or Current Inputs
Figure 5. Basic Unity-Gain Application
REV. D
(NOTE: Circuit figures shown on this page are for SIP-style packages. Refer to
Page 3 for proper DIP package pinout.)
–5–
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