LT6119-1/LT6119-2
16
611912f
For more information www.linear.com/LT6119-1
applicaTions inForMaTion
number can be multiplied by the θ
JA
value, 160°C/W, to
find the maximum expected die temperature. Proper heat
sinking and thermal relief should be used to ensure that
the die temperature does not exceed the maximum rating.
LE Pin
The LE pin is used to enable the comparator’s output latch.
When the LE pin is high, the output latch is enabled and
the comparator outputs will stay low once tripped. When
LE is low, the comparator output latches are disabled and
the comparators operate transparently. To continuously
operate the comparators transparently, the LE pin should
be grounded. Do not leave the LE pin floating.
Power-On Reset
During start-up, the state of the comparator outputs can
-
not be
guaranteed. To
guarantee the correct state of the
comparators outputs on start-up, a power-on reset (POR) is
required. A POR can be implemented by holding the LE pin
low until the LT6119 is in such a state that the comparator
outputs are stable. This can be achieved by using an RC
network between the LE, V
+
and GND, as shown in Figure 7.
When power
is applied to the LT6119, the RC network
causes the voltage on the LE pin to remain below the V
IL
(0.5V) threshold long enough for the comparator outputs
to settle into the correct state. The LE pin should remain
below 0.5V for at least 100µs after power-up in order to
Output Current Limitations Due to Power Dissipation
The LT6119 can deliver a continuous current of 1mA to the
OUTA pin. This current flows through R
IN
and enters the
current sense amplifier via the SENSEHI pin. The power
dissipated in the LT6119 due to the output signal is:
P
OUT
= (V
SENSEHI
– V
OUTA
) • I
OUTA
Since V
SENSEHI
≈ V
+
, P
OUTA
≈ (V
+
– V
OUTA
) • I
OUTA
There is also power dissipated due to the quiescent power
supply current:
P
S
= I
S
• V
+
The comparator output current flows into the comparator
output pin and out of the V
–
pin. The power dissipated in
the LT6119 due to each comparator is often insignificant
and can be calculated as follows:
P
OUTC1,C2
= (V
OUTC1,C2
– V
–
) • I
OUTC1,C2
The total power dissipated is the sum of these
dissipations:
P
TOTAL
= P
OUTA
+ P
OUTC1
+ P
OUTC2
+ P
S
At maximum supply and maximum output currents, the
total power dissipation can exceed
100mW. This will
cause significant heating of the LT6119 die. In order to
prevent damage to the LT6119, the maximum expected
dissipation in each application should be calculated. This
Figure 7. RC Network Achieves Power-On Reset
LE
LT6119
R
110k
60V
V
+
V
LE
C
0.1µF
611912 F07
