Datasheet

7
LTC3834-1
38341f
UU
U
PI FU CTIO S
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-
(DHC Package/GN Package)
TYPICAL PERFOR A CE CHARACTERISTICS
UW
T
A
= 25ºC, unless otherwise noted.
Shutdown Current vs Temperature
INTV
CC
vs Load Current
TEMPERATURE (°C)
4
5
7
45
38341 G27
3
2
0–15–30–45 15
30 60 75 90
1
0
6
SHUTDOWN CURRENT (μA)
LOAD CURRENT (mA)
5.0
5.2
5.3
50
38341 G26
4.9
4.8
2010030
40 60
4.7
4.6
5.1
INTV
CC
VOLTAGE (V)
V
IN
= 12V