Datasheet

LTC6101/LTC6101HV
14
6101fh
APPLICATIONS INFORMATION
Output Filtering
The output voltage, V
OUT
, is simply I
OUT
• Z
OUT
. This
makes fi ltering straightforward. Any circuit may be used
which generates the required Z
OUT
to get the desired fi lter
response. For example, a capacitor in parallel with R
OUT
will give a low pass response. This will reduce unwanted
noise from the output, and may also be useful as a charge
reservoir to keep the output steady while driving a switch-
ing circuit such as a mux or ADC. This output capacitor
in parallel with an output resistor will create a pole in the
output response at:
f
–3dB
=
1
2•π •R
OUT
•C
OUT
Useful Equations
Input Voltage: V
SENSE
= I
SENSE
•R
SENSE
Voltage Gain:
V
OUT
V
SENSE
=
R
OUT
R
IN
Current Gain:
I
OUT
I
SENSE
=
R
SENSE
R
IN
Transconductance:
I
OUT
V
SENSE
=
1
R
IN
Transimpedance:
V
OUT
I
SENSE
= R
SENSE
•
R
OUT
R
IN
Figure 5. V
+
Powered Separately from
Load Supply (V
BATT
)
Figure 6. LTC6101 Supply Current
Monitored with Load
LTC6101
R
OUT
V
OUT
6101 F05
R
IN
LOAD
V
+
R
SENSE
V
BATTERY
–
+
V
+
V
–
OUT
–IN+IN
LTC6101
R
OUT
V
OUT
6101 F06
R
IN
LOAD
V
+
R
SENSE
–
+
V
+
V
–
OUT
–IN+IN
Input Common Mode Range
The inputs of the LTC6101 can function from 1.5V below
the positive supply to 0.5V above it. Not only does this
allow a wide V
SENSE
range, it also allows the input refer-
ence to be separate from the positive supply (Figure 5).
Note that the difference between V
BATT
and V
+
must be no
more than the common mode range listed in the Electrical
Characteristics table. If the maximum V
SENSE
is less than
500mV, the LTC6101 may monitor its own supply current,
as well as that of the load (Figure 6).