LTC3867
8
3867f
PIN FUNCTIONS
TYPICAL PERFORMANCE CHARACTERISTICS
Shutdown Current vs Input Voltage Shutdown Current vs Temperature
RUN (Pin 1): Run Control Input. A voltage above 1.22V
turns on the IC. There is a 1µA pull-up current on this pin.
Once the RUN pin rises above the 1.22V threshold the
pull-up increases to 5µA.
DIFF
+
(Pin 2): Remote Sense Differential Amplifier Non-
inverting Input. Connect to Feedback divider center tap
with the divider across the output load.
DIFF
–
(Pin 3): Remote Sense Differential Amplifier Invert-
ing Input. Connect to sense ground at the output load.
DIFFOUT (Pin 4): Differential Amplifier Output.
V
FB
(Pin 5): Error Amplifier Inverting Input. Connect to
DIFFOUT for remote V
OUT
sensing.
I
TH
(Pin 6): Current Control Thresholds and Error Amplifier
Compensation Point. The current comparator’s threshold
increases with the I
TH
control voltage.
IFAST (Pin 7): Programming Pin for Nonlinear Control Trip
Threshold. A resistor to SGND programs the trip threshold
for the nonlinear control circuit. Connect to INTV
CC
to
disable this function.
TK/SS (Pin 8): Output Voltage Tracking and Soft-Start Input.
The voltage ramp rate at this pin sets the voltage ramp
rate of the output. A capacitor to ground accomplishes
soft-start. This pin has a 1.25µA pull-up current.
SENSE
+
(Pin 9): Current Sense Comparator Input. The (+)
input to the current comparator is normally connected to
the midpoint of the inductor’s parallel RC sense circuit or
the inductor side of the current sensing resistor.
SENSE
–
(Pin 10): Current Sense Comparator Input. The
(–) input to the current comparator is normally connected
to V
OUT
.
I
LIM
(Pin 11): Current Comparator Sense Voltage Limit
Selection Pin.
ITSD (Pin 12): Inductor Temperature-Based Thermal Shut-
down. Sources a 20µA current. Use a Murata PRF18 series
PTC to ground. Grounding this pin disables this function.
ITEMP (Pin 13): Input of the Temperature Sensing Com-
parators. Connect this pin to an external NTC resistor
placed near the inductor. Floating this pin disables the
DCR temperature compensation function.
EXTV
CC
(Pin 14): External Power Input to an Internal Switch
Connected to INTV
CC
. This switch closes and supplies the
IC power, bypassing the internal 5.3V regulator, whenever
EXTV
CC
is higher than 4.7V. Do not exceed 6V.
V
IN
(Pin 15): Main Input Supply. Decouple this pin to
PGND with a capacitor (0.1µF to 1µF)
INPUT VOLTAGE (V)
5 10
0
20
15
25
30
3867 G19
10
40
30
20
35
40
TEMPERATURE (°C)
–50 –25
10
30
0
50
75
3867 G20
20
50
40
25
100
125
TK/SS Pull-Up Current
vs Temperature
TEMPERATURE (°C)
–50
1.0
1.1
1.2
1.3
–25 0 25 50
3867 G13
75 100 125
