Iin And Iout Current Monitoring And Limiting - Linear Technology Analog Devices LT8708 Datasheet

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