Datasheet

LTC6102
LTC6102-1/LTC6102HV
17
6102fe
For more information www.linear.com/LTC6102
Figure 6. V
+
Powered Separately from Load Supply (V
BAT
)
6102 F06
LTC6102
R
OUT
V
OUT
R
IN
V
BAT
LOAD
(V
+
– 2V) TO V
+
R
SENSE
V
+
V
–
OUT
+IN
V
+
–INF
–INS
V
REG
0.1µF
–
+
applicaTions inForMaTion
Output Filtering
The output voltage, V
OUT
, is simply I
OUT
• Z
OUT
. This
makes filtering straightforward. Any circuit may be used
which generates the required Z
OUT
to get the desired filter
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
RC
dB
OUT OUT
–
•• •
3
1
2
=
π
Useful Equations
Input Voltage: V
Voltage
SENSE
= IR
SENSESENSE
•
GGain:
V
V
Current Gain:
I
I
OUT
SENSE
OUT
S
=
R
R
OUT
IN
EENSE
OUT
SENSE
Transconductance:
I
V
=
=
R
R
SENSE
IN
11
R
R
R
R
IN
SENSE
OUT
Transimpedance:
V
I
OUT
SENSE
= •
IIN
Input Sense Range
The inputs of the LTC6102 can function from V
+
to (V
+
– 2V).
Not only does this allow a wide V
SENSE
range, it also allows
the input reference to be separate from the positive supply
(Figure 6). Note that the difference between V
BAT
and V
+
must be no more than the input sense voltage range listed
in the Electrical Characteristics table.
Monitoring Voltages Above V
+
and Level Translation
The LTC6102 may be configured to monitor voltages that are
higher than its supply, provided that the negative terminal
of the input voltage is within the input sense range of the
LTC6102. Figure 7 illustrates a circuit in which the LTC6102
has its supply pin tied to the lower potential terminal of the
sense resistor instead of the higher potential terminal. The
Figure 7. LTC6102 Supply Current Monitored with Load
–INF
–INS
LTC6102
R
OUT
V
OUT
6102 F07
R
IN
LOAD
V
BAT
R
SENSE
V
+
V
–
OUT
+IN
V
REG
0.1µF
–
+
operation of the LTC6102 is such that the –INS and –INF
pins will servo to within a few microvolts of +IN, which is
shorted to V
+
. Since the input sense range of the LTC6102
includes V
+
, the circuit will operate properly. The voltage
across R
SENSE
will be held across R
IN
by the LTC6102,
causing current V
SENSE
/R
IN
to flow to R
OUT
. In this case,
the supply current of the LTC6102 is also monitored, as
it flows through R
SENSE
.
Because the voltage across R
SENSE
is not restricted to
the sense range of the LTC6102 in this circuit, V
SENSE
can be large compared to the allowed sense voltage. This
facilitates the sensing of very large voltages, provided
that R
IN
is chosen so that V
SENSE
/R
IN
does not exceed