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© Andigilog, Inc. 2003
www.andigilog.com
70A03201-004
aTS20
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The aTS20 will handle sizable capacitive loads up to
300pF without any special considerations.
In an
extremely noisy environment it may be advisable to add
some filtering to minimize noise in the output voltage. It is
also recommended that a 0.1µF bypass capacitor be
added between the supply voltage and ground. This is
due to the instant current demand caused by switching
CMOS transistors. Normally it is unadvisable to put a
sufficiently
large
supply
(particularly
in
portable
electronics) to be able to handle the dynamic currents of
CMOS transistors. It is a much simpler solution to use a
bypass capacitor to sustain the supply voltage during this
short demand period.
In environments that are particularly noisy it may be
necessary to add a low-pass filter network to the output
of the device. As shown in Figure 8, a 1µF capacitor in
addition to the output impedance of the device and a
200
Ω series resistor for a low-pass filter that will pass the
slow thermal time constant of the aTS20, while filtering
the higher frequency noise. The response time of the
aTS20 can be affected by this filter network, therefore
values for CFILTER < 1500pF are recommended.
aTS20
0.1µF
Bypass
Cap
V
DD
GND
V
OUT
C
FILTER
R
FILTER
C
L
0.1µF
Bypass
Cap
V
DD
GND
V
OUT
C
FILTER
R
FILTER
C
L
aTS20
aTS20
aTS20
0.1µF
Bypass
Cap
V
DD
GND
V
OUT
C
FILTER
R
FILTER
C
L
0.1µF
Bypass
Cap
V
DD
GND
V
OUT
C
FILTER
R
FILTER
C
L
aTS20
aTS20
Resistor / Capacitor Combinations for Figure 8 Filter Network
RFILTER
CFILTER
200
Ω
1 µF
470
Ω
0.1 µF
680
Ω
0.01 µF
1000
Ω
1000 pF
10k
Ω
100pF
100k
Ω
10pF
Figure 8. aTS20 with Filter Network for Noisy Environments or for Capacitive Loads
Greater than 300pF
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