AD210 L-COM, AD210 Datasheet - Page 6

• Manufacturer Part Number: AD210
• Description: FOM100 SERIES UNIV LC ADPTR
• Manufacturer: L-COM

AD210
Isolated Power: The AD210 provides isolated power at the
input and output ports. This power is useful for various signal
conditioning tasks. Both ports are rated at a nominal 15 V at
5 mA.
The load characteristics of the isolated power supplies are
shown in Figure 15. For example, when measuring the load
rejection of the input isolated supplies V
between +V
the individual load rejection characteristics of the input and the
output supplies, respectively.
There is also some effect on either isolated supply when loading
the other supply. The curve labeled CROSSLOAD indicates the
sensitivity of either the input or output supplies as a function of
the load on the opposite supply.
Lastly, the curves labeled V
neous indicate the load characteristics of the isolated power sup-
plies when an equal load is placed on both supplies.
The AD210 provides short circuit protection for its isolated
power supplies. When either the input supplies or the output
supplies are shorted to input common or output common,
respectively, no damage will be incurred, even under continuous
application of the short. However, the AD210 may be damaged
if the input and output supplies are shorted simultaneously.
Under any circumstances, care should be taken to ensure that
the power supplies do not accidentally become shorted.
Figure 16a. Isolated Supply Ripple vs. Load
(External 4.7 F Bypass)
Figure 15. Isolated Power Supplies vs. Load
100
75
50
25
30
25
20
30
0
30
0
ISS
0
and –V
1
ISS
. The curves labeled V
2
OSS
CURRENT – mA
5
LOAD – mA
simultaneous and V
3
4
CROSSLOAD
ISS
V
V
V
V
, the load is placed
OSS
OSS
ISS
ISS
5
SIMULTANEOUS
SIMULTANEOUS
ISS
10
and V
ISS
6
+V
–V
+V
–V
simulta-
OSS
ISS
ISS
OSS
OSS
7
are
–6–
The isolated power supplies exhibit some ripple which varies as
a function of load. Figure 16a shows this relationship. The
AD210 has internal bypass capacitance to reduce the ripple to a
point where performance is not affected, even under full load.
Since the internal circuitry is more sensitive to noise on the
negative supplies, these supplies have been filtered more heavily.
Should a specific application require more bypassing on the iso-
lated power supplies, there is no problem with adding external
capacitors. Figure 16b depicts supply ripple as a function of
external bypass capacitance under full load.
APPLICATIONS EXAMPLES
Noise Reduction in Data Acquisition Systems: Transformer
coupled isolation amplifiers must have a carrier to pass both ac
and dc signals through their signal transformers. Therefore,
some carrier ripple is inevitably passed through to the isolator
output. As the bandwidth of the isolator is increased more of the
carrier signal will be present at the output. In most cases, the
ripple at the AD210’s output will be insignificant when com-
pared to the measured signal. However, in some applications,
particularly when a fast analog-to-digital converter is used fol-
lowing the isolator, it may be desirable to add filtering; other-
wise ripple may cause inaccurate measurements. Figure 17
shows a circuit that will limit the isolator’s bandwidth, thereby
reducing the carrier ripple.
Self-Powered Current Source
The output circuit shown in Figure 18 can be used to create a
self-powered output current source using the AD210. The 2 k
resistor converts the voltage output of the AD210 to an equiva-
V
SIG
Figure 16b. Isolated Power Supply Ripple vs. Bypass
Capacitance (Volts p-p, 1 MHz Bandwidth, 5 mA Load)
17
16
19
18
14
15
100mV
10mV
1mV
1V
0.1µF
+V
–V
ISS
ISS
Figure 17. 2-Pole, Output Filter
+15V
30
1µF
29
AD210
CAPACITANCE
+V
–V
OSS
OSS
10µF
1
2
3
4
R
R (k ) =
0.001µF
100µF
R
(
(
(
f
C
–V
–V
112.5
+V
+V
(kHz)
ISS
OSS
ISS
OSS
AD542
–V
+V
OSS
)
)
)
OSS
0.002µF
REV. A
V
OUT