LT8708
42
Rev 0
For more information
V
OVIN+
and V
OVIN
– are the rising and falling V
IN
over-
voltage thresholds.
V
UVOUT+
and V
UVOUT
– are the rising and falling V
OUT
undervoltage thresholds.
R
IN1-4
and R
OUT1-4
are shown in Figure 13 and Figure 14.
V
HYSMON
is the VINHIMON and VOUTLOMON hyster-
esis voltage. Typical value is 24mV.
I
HYSMON
is the VINHIMON and VOUTLOMON hysteresis
current. Typical value is 1μA.
If unused, tie VINHIMON to GND and/or VOUTLOMON
to LDO33.
Note: after the resistor values are selected, make sure to
check that the FBIN and VOUTLOMON voltages are be-
low their ABSMAX values when V
IN
and V
OUT
are at their
maximum, respectively.
I
IN
AND I
OUT
CURRENT MONITORING AND LIMITING
The LT8708 has independent I
IN
and I
OUT
current monitors
that can monitor and limit the respective currents in both
positive and negative directions. Figure 15 and Figure 16
illustrate the operation of the current monitor circuits.
The remaining discussion refers to the I
IN
current monitor
circuit of Figure 15. All discussion and equations are also
applicable to the I
OUT
current monitor circuit, substituting
pin and device names as appropriate.
Current Monitoring: The IMON_INP and IMON_INN pins
can be used to monitor I
IN
in the forward and reverse
directions, respectively. When configured as shown in
Figure 15, the IMON_INP and IMON_INN voltages are
proportional to I
IN
. V
IMON_INP
is proportional to the posi-
tive I
IN
current, increasing as I
IN
becomes more positive.
V
IMON_INN
is proportional to the negative I
IN
current,
increasing as I
IN
becomes more negative.
APPLICATIONS INFORMATION
Figure 16. I
OUT
Current Monitor and Limit
–
+
EA1
IMON_INP
IMON_INN
8708 F15
C
IMON_INP
R
IMON_INP
CSPIN
R
SENSE1
FROM
SYSTEM
V
IN
TO
CONTROLLER
V
IN
CSNIN
LT8708
I
IN
V
C
1.21V
–
+
EA5
1.209V
–
+
g
m
= 1m
Ω
A3
C
IMON_INN
R
IMON_INN
+
–
20μA
20μA
–
+
EA2
IMON_OP
IMON_ON
8708 F16
C
IMON_OP
R
IMON_OP
CSPOUT
R
SENSE2
FROM
CONTROLLER
V
OUT
TO
SYSTEM
V
OUT
CSNOUT
LT8708
I
OUT
V
C
1.21V
–
+
EA6
1.209V
–
+
g
m
= 1m
Ω
A1
C
IMON_ON
R
IMON_ON
+
–
20μA
20μA
Figure 15. I
IN
Current Monitor and Limit
