LTC3834 Linear Technology, LTC3834 Datasheet - Page 8

• Manufacturer Part Number: LTC3834
• Description: Synchronous Step-Down Controller
• Manufacturer: Linear Technology

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PIN FUNCTIONS
LTC3834
CLKOUT (Pin 1/Pin 19): Open-Drain Output Clock Signal
available to daisy-chain other controller ICs for additional
MOSFET driver stages/phases.
PLLLPF (Pin 2/Pin 20): The phase-locked loop’s lowpass
fi lter is tied to this pin when synchronizing to an external
clock. Alternatively, tie this pin to GND, V
fl oating to select 250kHz, 530kHz or 400kHz switching
frequency.
I
Regulator Compensation Points. The current comparator
trip point increases with this control voltage.
TRACK/SS (Pin 4/Pin 2): External Tracking and Soft-Start
Input. The LTC3834 regulates the V
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 fi nal regulated
output voltage. Alternatively, a resistor divider on another
voltage supply connected to this pin allows the LTC3834
output to track the other supply during start-up.
V
back voltage from an external resistive divider across
the output.
SGND (Pin 6/Pin 4): Small-Signal Ground. Must be routed
separately from high current grounds to the common (–)
terminals of the input capacitor.
PGND (Pin 7/Pin 5): Driver Power Ground. Connects to the
source of bottom (synchronous) N-channel MOSFET, anode
of the Schottky rectifi er and the (–) terminal of C
BG (Pin 8/Pin 6): High Current Gate Drive for Bottom
(Synchronous) N-Channel MOSFET. Voltage swing at this
pin is from ground to INTV
INTV
Dropout Regulator. The driver and control circuit are
powered from this voltage source. Must be decoupled
to power ground with a minimum of 4.7μF tantalum or
ceramic capacitor.
EXTV
LDO Connected to INTV
bypassing the internal LDO powered from V
EXTV
8
TH
FB
(Pin 3/Pin 1): Error Amplifi er Outputs and Switching
(Pin 5/Pin 3): Receives the remotely sensed feed-
CC
CC
CC
(Pin 9/Pin 7): Output of the Internal Linear Low
(Pin 10/Pin 8): External Power Input to an Internal
is higher than 4.7V. See EXTV
CC
. This LDO supplies V
CC
(FE/UFD)
.
FB
voltage to the smaller
CC
Connection in
IN
IN
whenever
CC
or leave
IN
power,
.
the Applications Information section. Do not exceed 10V
on this pin.
V
should be tied between this pin and the signal ground
pin.
SW (Pin 12/Pin 10): Switch Node Connections to Inductor.
Voltage swing at this pin is from a Schottky diode (external)
voltage drop below ground to V
TG (Pin 13/Pin 11): High Current Gate Drive for Top
N-Channel MOSFET. These are the outputs of fl oating drivers
with a voltage swing equal to INTV
on the switch node voltage SW.
BOOST (Pin 14/Pin 12): Bootstrapped Supply to the
Topside Floating Driver. A capacitor is connected between
the BOOST and SW pins and a Schottky diode is tied
between the BOOST and INTV
BOOST pin is from INTV
RUN (Pin 15/Pin 13): Digital Run Control Input for
Controller. Forcing this pin below 0.7V shuts down all
controller functions, reducing the quiescent current that
the LTC3834 draws to approximately 4μA.
SENSE
Current Comparator.
SENSE
Current Comparator. The I
offsets between the SENSE
tion with R
PGOOD (Pin 18/Pin 16): Open-Drain Logic Output. PGOOD
is pulled to ground when the voltage on the V
within ±10% of its set point.
PLLIN/MODE (Pin 19/Pin 17): External Synchronization
Input to Phase Detector and Forced Continuous Control
Input. When an external clock is applied to this pin, the
phase-locked loop will force the rising TG signal to be
synchronized with the rising edge of the external clock. In
this case, an R-C fi lter must be connected to the PLLLPF
pin. When not synchronizing to an external clock, this
input determines how the LTC3834 operates at light loads.
Pulling this pin below 0.7V selects Burst Mode operation.
Tying this pin to INTV
IN
(Pin 11/Pin 9): Main Supply Pin. A bypass capacitor
–
+
(Pin 16/Pin 14): The (–) Input to the Differential
(Pin 17/Pin 15): The (+) Input to the Differential
SENSE
set the current trip threshold.
CC
forces continuous inductor current
CC
TH
–
to (V
and SENSE
CC
pin voltage and controlled
pins. Voltage swing at the
IN
IN
CC
.
+ INTV
– 0.5V superimposed
+
pins in conjunc-
CC
).
FB
pin is not
3834fb