LT6108-1/LT6108-2
25
610812fa
TYPICAL APPLICATIONS
An external latch is implemented with positive feedback.
R6 and C1 provide a reset pulse on power-up. The time
constant formed by R6 and C1 should be set slower than
that of the supply. Optional components R9 and Q1 dis-
charge capacitor C1 when the supply and/or ground are
disconnected. This ensures that when the power supply
and/or ground are restored, capacitor C1 can fully recharge.
While C1 is charging, the NOR gate output is low, ensuring
that the comparator powers up in the correct state. These
optional components are particularly useful if the power
and/or ground connections are intermittent, as can occur
when PCB are plugged into a connector. R4 and R5 are
optional and minimize the movement of the rising input
threshold voltage.
–
+
V
+
V
–
V
–
4
610812 TA06
V
+
400mV
REFERENCE
V
+
R
IN
100Ω
R
SENSE
I
LOAD
OUTA 6
INC 5
VTH
7
SENSEHI
LT6108-2
SENSELO
OUTC
8
1
3
R7
9.53k
R8
499Ω
R1
24.9k
R2
200k
V
DD
R6
1M
*OPTIONAL COMPONENT
C1
0.1µF
Q1*
2N2222
R4*
3.4k
R5*
100k
R9*
30k
R3
10k
–
+
LT6108-2 with External Latch and Power-On Reset or Disconnect
The input rising edge threshold which causes the output
to transition from high to low is:
V
TH R
( )
= 400mV if R4 = R5 •
400mV
V
DD
– 400mV
The input falling edge which causes the output to transi-
tion from low to high is:
V
TH F
( )
= 390mV • R1 •
1
R1
+
1
R2+R4||R5
–
V
DD
• R1
R2+R4||R5
