Linear Technology Analog Devices LT8708 Datasheet page 41

APPLICATIONS INFORMATION
V
IN
R
HIMON1
R
HIMON3
R
HIMON2
(a) Resistor Divider for VINHIMON
V
OUT
R
LOMON1
R
LOMON3
R
LOMON2
(b) Resistor Divider for VOUTLOMON
Figure 12.
where:
I is the desired current through the resistor string.
FBDIV
50μA – 100μA is a good value.
V and V are the desired regulation voltages.
IN OUT
V
IN
R
IN1
R
IN2
R
IN4
R
IN3
Figure 13. Single Divider for VINHIMON and FBIN
V
OUT
R
OUT1
R
OUT4
R
OUT2
R
OUT3
Figure 14. Single Divider for VOUTLOMON and FBOUT
LT8708
VINHIMON
LT8708
VOUTLOMON
8708 F12
FBIN
LT8708
VINHIMON
8708 F13
VOUTLOMON
LT8708
FBOUT
8708 F14
For more information
2. Connect a resistor divider between V
HIMON and GND to configure the V
overvoltage thresholds (see Figure 13). Connect a
resistor divider between V
and GND to configure the V
voltage thresholds (see Figure 14).
Use the following equations to calculate the resistor values:
1.207 • V
IN
R
=
IN3
V •I
FBDIV
+
OVIN
⎛
⎜
R = V • R •
IN1 IN3 ⎜ ⎜
+
OVIN
1.207
⎝
(V – V )
IN
+
OVIN
R • R
=
IN2 IN3
V
IN
R
=
IN4
⎛
[(R + R ) •I
⎜
IN1 IN2 HYSMON
⎜
⎜ ⎜ V
OVIN
⎝
⎛
⎛ ⎞
(V
V
⎜
⎜ HYSMON ⎟
– ⎟ ⎟ –
⎜
⎜ ⎜
I
⎜
HYSMON
⎝ ⎠
⎝
1.207
R
=
OUT3
I
FBDIV
⎛
⎜
R = V R •
⎜
OUT1 OUT• OUT3
1.207
⎜
⎝
(V – V
OUT
UVOUT
R
=
OUT2
V
–
UVOUT
R
=
OUT4
⎛
(R •I + V
⎜
OUT1 HYSMON
⎜
⎜ ⎜
V
UVOUT
⎝
⎛
⎛ ⎞ (V
V
⎜
⎜ ⎟
HYSMON
– ⎟ ⎟ –
⎜
⎜ ⎜
I
⎜
HYSMON
⎝ ⎠
⎝
www.analog.com
LT8708
, FBIN, VIN-
IN
regulation and
IN
VOUTLOMON, FBOUT
OUT,
regulation and under-
OUT
⎞
1 1
⎟
–
⎟ ⎟
V
IN
⎠
+ V – V ] • 1.207
–
OVIN
+
OVIN
•I
HYSMON
+
⎞
– 1.207) • R
⎟
IN3
+
OVIN
⎟
V
⎟
+
OVIN
⎠
⎞
1 1
⎟
–
⎟
V
⎟
–
UVOUT
⎠
)
–
• R
OUT3
– V ) • 1.207
+
–
UVOUT
UVOUT
•I
–
HYSMON
⎞
– 1.207) • R
– ⎟
OUT3
UVOUT
⎟
V
⎟
–
UVOUT
⎠
41
⎞
⎟
⎟
⎟ ⎟
⎠
⎞
⎟
⎟
⎟ ⎟
⎠
Rev 0