LTC3867_15 Datasheet, PDF (8/36 Pages) Linear Technology – Low IQ, Dual 2-Phase Synchronous Step-Down Controller

LTC3867
TYPICAL PERFORMANCE CHARACTERISTICS
TK/SS Pull-Up Current
vs Temperature
1.4
1.3
1.2
1.1
1.0
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
3867 G13
Shutdown Current vs Input Voltage
50
40
30
20
10
0
5 10 15 20 25 30 35 40
INPUT VOLTAGE (V)
3867 G19
Shutdown Current vs Temperature
60
50
40
30
20
10
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
3867 G20
PIN FUNCTIONS
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.
8
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)
3867f