LT6108-1/LT6108-2
22
610812fa
Figure 17. Amplifier Enable Response
current. Figure17 shows this behavior and the impact it has
on V
OUTA
. Circuitry connected to OUTA can be protected
from these transients by using an external diode to clamp
V
OUTA
, or a capacitor to filter V
OUTA
.
APPLICATIONS INFORMATION
Power Up
After powering on the LT6108-1, the comparator must
be reset in order to guarantee a valid state at its output.
Fast supply ramps may cause a supply current transient
during start-up as shown in the Typical Performance
Characteristics. This current can be lowered by reducing
the edge speed of the supply.
Reverse-Supply Protection
The LT6108 is not protected internally from external rever-
sal of supply polarity. To prevent damage that may occur
during this condition, a Schottky diode should be added
in series with V
–
(Figure 18). This will limit the reverse
current through the LT6108. Note that this diode will limit
the low voltage operation of the LT6108 by effectively
reducing the supply voltage to the part by V
D
.
Also note that the comparator reference, comparator
output and EN/RST input are referenced to the V
–
pin. In
order to preserve the precision of the reference and to
avoid driving the comparator inputs below V
–
, R2 must
connect to the V
–
pin. This will shift the amplifier output
voltage up by V
D
. V
OUTA
can be accurately measured
50µs/DIV
0V
V
EN/RST
2V/DIV
0V
V
OUTA
2V/DIV
610812 F17
V
+
= 60V
R
IN
= 100Ω
R
OUT
= 10k
–
+
V
+
V
+
V
–
INC
V
–
4
V
D
+
–
V
OUTA
+
–
610812 F18
OUTA 6
7
5
V
+
V
+
SENSEHI
LT6108-1
R
IN
R
SENSE
I
LOAD
V
DD
V
DD
SENSELO
OUTC3
EN/RST
2
1
8
400mV
REFERENCE
R3
R1
R2
V
DD
–
+
EN Pin (LT6108-2)
When this pin is pulled high, the LT6108-2 is enabled. When
the enable pin is pulled low for longer than 40µs typically,
the LT6108-2 will enter the shutdown mode.
Figure 18. Schottky Prevents Damage During Supply Reversal
