LTC6104
13
6104f
Reverse Supply Protection
Some applications may be tested with reverse-polarity
supplies due to an expectation of this type of fault during
operation. The LTC6104 is not protected internally from
external reversal of supply polarity. To prevent damage that
may occur during this condition, a Schottky diode should
be added in series with V
–
(Figure 6). This will limit the
reverse current through the LTC6104. Note that this diode
will limit the low voltage performance of the LTC6104 by
effectively reducing the supply voltage to the part by V
D
.
Keep this in mind when choosing an output resistor and
voltage reference.
In addition, if the output of the LTC6104 is wired to a
device that will effectively short it to high voltage (such as
through an ESD protection clamp) during a reverse sup-
ply condition, the LTC6104’s output should be connected
through a resistor or Schottky diode (Figure 7).
Response Time
The LTC6104 is designed to exhibit fast response to inputs
for the purpose of circuit protection or signal transmission.
This response time will be affected by the external circuit
in two ways: delay and speed.
For unidirectional applications, if the output current is
very low and an input transient occurs, there may be an
increased delay before the output voltage starts to change.
This can be improved by increasing the minimum output
current, either by increasing R
SENSE
or by decreasing R
IN
.
The effect of increased output current is illustrated in the
step response curves in the Typical Performance Charac-
teristics section of this datasheet. Note that the curves are
labeled with respect to the initial output currents.
For bidirectional applications, there is a delay when output
current changes polarity. The delay time can be found
in the step response curves in the Typical Performance
Characteristics section of this data sheet.
Speed is also affected by the external circuit. In this case,
if the input changes very quickly, the internal amplifi er
and the internal output FET (Figure 1) will attempt to
maintain the internal loop, but may be slew rate limited.
This results in current fl owing through R
IN
and the internal
FET. This current slew rate will be determined by the ampli-
fi er and FET characteristics as well as the input resistor,
R
IN
. Using a smaller R
IN
will allow the output current to
increase more quickly, decreasing the response time at
the output. This will also have the effect of increasing
the maximum output current. Using a larger R
OUT
will
APPLICATIONS INFORMATION
Figure 6. Schottky Prevents Damage During Supply Reversal
Figure 7. Additional Resistor R1 Protects Output
During Supply Reversal
+
–
8 7 6
4
+INA
OUT
+
–
V
S
I
S
V
S
A
LTC6104
–INA –INB
R
IN
R
IN
TO
CHARGER/LOAD
R
SENSE
V
SENSE
+–
+INB
V
–
I
LOAD
+
CURRENT
MIRROR
+
–
5
B
R
OUT
D1
V
REF
6104 F06
V
OUT
+
–
1
+
–
8 7 6
4
+INA
OUT
R1
V
S
V
S
A
LTC6104
–INA –INB
R
IN
R
IN
TO
CHARGER/LOAD
R
SENSE
V
SENSE
+–
+INB
V
–
I
LOAD
+
CURRENT
MIRROR
+
–
5
B
R
OUT
D1
V
REF
6104 F07
+
–
1
ADC
