LTC1735I-1 Linear Technology, LTC1735I-1 Datasheet - Page 7

• Manufacturer Part Number: LTC1735I-1
• Description: High Efficiency Synchronous Step-Down Switching Regulator
• Manufacturer: Linear Technology

C
ground sets the operating frequency.
RUN/SS (Pin 2): Combination of Soft-Start and Run
Control Inputs. A capacitor to ground at this pin sets the
ramp time to full current output. The time is approximately
1.25s/ F. Forcing this pin below 1.5V causes the device to
be shut down. In shutdown all functions are disabled.
Latchoff overcurrent protection is also invoked via this pin
as described in the Applications Information section.
I
current comparator threshold increases with this control
voltage. Nominal voltage range for this pin is 0V to 2.4V.
PGOOD (Pin 4): Open-Drain Logic Output and Forced
Continuous/Synchronization Input. The PGOOD pin is
pulled to ground when the voltage on the V
not within 7.5% of its nominal set point. If power good
indication is not needed, this pin can be tied to ground to
force continuous synchronous operation. Clocking this
pin with a signal above 1.5V
oscillator to the external clock. Synchronization only
occurs while the main output is in regulation (PGOOD not
internally pulled low). When synchronized, Burst Mode
operation is disabled but cycle skipping is allowed at low
load currents. This pin requires a pull-up resistor for
power good indication. Do not connect this pin directly to
an external source (or INTV
this pin.
SENSE
SENSE
Built-in offsets between SENSE
conjunction with R
threshold.
V
external resistive divider across the output.
PI FU CTIO S
TH
OSC
OSENSE
U
(Pin 3): Error Amplifier Compensation Point. The
(Pin 1): External capacitor C
–
+
(Pin 5): The (–) Input to the Current Comparator.
(Pin 6): The (+) Input to the Current Comparator.
(Pin 7): Receives the feedback voltage from an
U
SENSE
U
set the inductor current trip
CC
P-P
). Do not exceed INTV
synchronizes the internal
+
and SENSE
OSC
from this pin to
OSENSE
–
pins in
pin is
CC
on
SGND (Pin 8): Small-Signal Ground. All small-signal
components such as C
the loop compensation resistors and capacitor(s) should
single-point tie to this pin. This pin should, in turn, connect
to PGND.
EXTV
INTV
ever EXTV
in Applications Information section. Do not exceed 7V on
this pin and ensure EXTV
PGND (Pin 10): Driver Power Ground. This pin connects
to the source of the bottom N-channel MOSFET, the anode
of the Schottky diode and the (–) terminal of C
BG (Pin 11): High Current Gate Drive for the Bottom
N-Channel MOSFET. Voltage swing at this pin is from
ground to INTV
INTV
Regulator and EXTV
circuits are powered from this voltage. Decouple to power
ground with a 1 F ceramic capacitor placed directly adja-
cent to the IC together with a minimum of 4.7 F tantalum
or other low ESR capacitor.
V
decoupled to power ground.
SW (Pin 14): Switch Node Connection to Inductor and
Bootstrap Capacitor. Voltage swing at this pin is from a
Schottky diode (external) voltage drop below ground to
V
BOOST (Pin 15): Supply to Topside Floating Driver. The
bootstrap capacitor is returned to this pin. Voltage swing
at this pin is from a diode drop below INTV
INTV
TG (Pin 16): High Current Gate Drive for Top N-Channel
MOSFET. This is the output of a floating driver with a
voltage swing equal to INTV
switch node voltage SW.
IN
IN
.
(Pin 13): Main Supply Pin. This pin must be closely
CC
CC
CC
CC
. This switch closes and supplies V
.
(Pin 12): Output of the Internal 5.2V Low Dropout
(Pin 9): Input to the Internal Switch Connected to
CC
is higher than 4.7V. See EXTV
CC
.
CC
OSC
Switch. The driver and control
CC
, C
is V
SS
CC
, the feedback divider plus
IN
superimposed on the
LTC1735-1
.
CC
CC
power when-
CC
connection
IN
to V
.
IN
7
+