
LTC6101/LTC6101HV
14
6101fh
APPLICATIONS INFORMATION
Output Filtering
The output voltage, VOUT, is simply IOUT ZOUT. This
makes ltering straightforward. Any circuit may be used
which generates the required ZOUT to get the desired lter
response. For example, a capacitor in parallel with ROUT
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 COUT
Useful Equations
Input Voltage: VSENSE =ISENSE RSENSE
Voltage Gain:
VOUT
VSENSE
=
ROUT
RIN
Current Gain:
IOUT
ISENSE
=
RSENSE
RIN
Transconductance:
IOUT
VSENSE
=
1
RIN
Transimpedance:
VOUT
ISENSE
= R
SENSE
ROUT
RIN
Figure 5. V+ Powered Separately from
Load Supply (VBATT)
Figure 6. LTC6101 Supply Current
Monitored with Load
LTC6101
ROUT
VOUT
6101 F05
RIN
LOAD
V+
RSENSE
VBATTERY
–
+
V+
V–
OUT
–IN
+IN
LTC6101
ROUT
VOUT
6101 F06
RIN
LOAD
V+
RSENSE
–
+
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 VSENSE range, it also allows the input refer-
ence to be separate from the positive supply (Figure 5).
Note that the difference between VBATT and V+ must be no
more than the common mode range listed in the Electrical
Characteristics table. If the maximum VSENSE is less than
500mV, the LTC6101 may monitor its own supply current,
as well as that of the load (Figure 6).