LTC3834-1 Datasheet, PDF (7/28 Pages) Linear Technology – 30μA IQ Synchronous Step-Down Controller

LTC3834-1
TYPICAL PERFOR A CE CHARACTERISTICS T_A = 25ºC, unless otherwise noted.
INTV_CC vs Load Current
5.3
5.2
V_IN = 12V
5.1
5.0
4.9
4.8
4.7
4.6
0
10 20 30 40 50 60
LOAD CURRENT (mA)
38341 G26
Shutdown Current vs Temperature
7
6
5
4
3
2
1
0
–45 –30 –15 0 15 30 45 60 75 90
TEMPERATURE (°C)
38341 G27
PI FU CTIO S (DHC Package/GN Package)
PLLLPF (Pin 1/Pin 1): The phase-locked loop’s lowpass
filter is tied to this pin when synchronizing to an external
clock. Alternatively, tie this pin to GND, INTV_CC or leave
floating to select 250kHz, 530kHz or 400kHz switching
frequency.
I_TH (Pin 2/Pin 2): Error Amplifier Outputs and Switching
Regulator Compensation Points. The current comparator
trip point increases with this control voltage.
TRACK/SS (Pin 3/Pin 3): External Tracking and Soft-
Start Input. The LTC3834-1 regulates the V_FB voltage
to the smaller of 0.8V or the voltage on the TRACK/
SS pin. A internal 1μA pull-up current source is connected
to this pin. A capacitor to ground at this pin sets the
ramp time to final regulated output voltage. Alternatively,
a resistor divider on another voltage supply connected
to this pin allows the LTC3834-1 output to track the
other supply during startup.
V_FB (Pin 4/Pin 4): Receives the remotely sensed feed-
back voltage from an external resistive divider across
the output.
SGND (Pin 5/Pin 5): Small Signal Ground. Must be routed
separately from high current grounds to the common (–)
terminals of the input capacitor.
PGND (Pin 6/Pin 6): Driver Power Ground. Connects to
the source of bottom (synchronous) N-channel MOSFET,
anode of the Schottky rectifier and the (–) terminal of C_IN.
BG (Pin 7/Pin 7): High Current Gate Drive for Bottom
(Synchronous) N-Channel MOSFET. Voltage swing at this
pin is from ground to INTV_CC.
INTV_CC (Pin 8/Pin 8): Output of the Internal Linear Low
Dropout Regulator. The driver and control circuits are
powered from this voltage source. Must be decoupled to
power ground with a minimum of 4.7μF tantalum or
ceramic capacitor.
V_IN (Pin 9/Pin 9): Main Supply Pin. A bypass capacitor
should be tied between this pin and the signal ground pin.
SW (Pin 10/Pin 10): Switch Node Connections to Induc-
tor. Voltage swing at this pin is from a Schottky diode
(external) voltage drop below ground to V_IN.
TG (Pin 11/Pin 11): High Current Gate Drive for Top N-
Channel MOSFET. These are the outputs of floating driv-
ers with a voltage swing equal to INTV_CC – 0.5V superim-
posed on the switch node voltage SW.
BOOST (Pin 12/Pin 12): Bootstrapped Supply to the Top
Side Floating Driver. A capacitor is connected between the
BOOST and SW pins and a Schottky diode is tied between
the BOOST and INTV_CC pins. Voltage swing at the BOOST
pin is from INTV_CC to (V_IN + INTV_CC).
RUN (Pin 13/Pin 13): Digital Run Control Input for Con-
troller. Forcing this pin below 0.7V shuts down all control-
38341f
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