LTC1628 LINER [Linear Technology], LTC1628 Datasheet - Page 8

• Manufacturer Part Number: LTC1628
• Description: High Efficiency, 2-Phase Synchronous Step-Down Switching Regulators
• Manufacturer: LINER [Linear Technology]

LTC1628/LTC1628-PG
PI FU CTIO S
RUN/SS1, RUN/SS2 (Pins 1, 15): Combination of soft-
start, run control inputs and short-circuit detection timers.
A capacitor to ground at each of these pins sets the ramp
time to full output current. Forcing either of these pins
back below 1.0V causes the IC to shut down the circuitry
required for that particular controller. Latchoff overcurrent
protection is also invoked via this pin as described in the
Applications Information section.
SENSE1
Differential Current Comparators. The I
controlled offsets between the SENSE
in conjunction with R
SENSE1
Differential Current Comparators.
V
sensed feedback voltage for each controller from an
external resistive divider across the output.
FREQSET (Pin 5): Frequency Control Input to the Oscilla-
tor. This pin can be left open, tied to ground, tied to INTV
or driven by an external voltage source. This pin can also
be used with an external phase detector to build a true
phase-locked loop.
STBYMD (Pin 6): Control pin that determines which cir-
cuitry remains active when the controllers are shut down
and/or provides a common control point to shut down
both controllers. See the Operation section for details.
FCB (Pin 7): Forced Continuous Control Input. This input
acts on the first controller (or both controllers depending
upon the FLTCPL pin—see pin description), and is
normally used to regulate a secondary winding. Pulling
this pin below 0.8V will force continuous synchronous
operation for the first and optionally the second control-
ler. Do not leave this pin floating.
I
ing Regulator Compensation Point. Each associated chan-
nels’ current comparator trip point increases with this
control voltage.
8
TH1,
OSENSE1
U
I
TH2
+
–
, SENSE2
, SENSE2
, V
(Pins 8, 11): Error Amplifier Output and Switch-
U
OSENSE2
+
–
U
(Pins 4, 12): Receives the remotely-
SENSE
(Pins 2, 14): The (+) Input to the
(Pins 3, 13): The (–) Input to the
set the current trip threshold.
–
th
and SENSE
pin voltage and
+
pins
CC
SGND (Pin 9): Small Signal Ground common to both
controllers, must be routed separately from high current
grounds to the common (–) terminals of the C
capacitors.
3.3V
supplying 10mA DC with peak currents as high as 50mA.
PGND (Pin 20): Driver Power Ground. Connects to the
sources of bottom (synchronous) N-channel MOSFETs, an-
odes of the Schottky rectifiers and the (–) terminal(s) of C
INTV
Dropout Regulator and the EXTV
control circuits are powered from this voltage source. Must
be decoupled to power ground with a minimum of 4.7 F
tantalum or other low ESR capacitor. The INTV
standby function is determined by the STBYMD pin.
EXTV
Switch Connected to INTV
supplies V
regulator, whenever EXTV
EXTV
7V on this pin.
BG1, BG2 (Pins 23, 19): High Current Gate Drives for
Bottom (Synchronous) N-Channel MOSFETs. Voltage
swing at these pins is from ground to INTV
V
be tied between this pin and the signal ground pin.
BOOST1, BOOST2 (Pins 25, 18): Bootstrapped Supplies
to the Top Side Floating Drivers. Capacitors are connected
between the boost and switch pins and Schottky diodes
are tied between the boost and INTV
at the boost pins is from INTV
SW1, SW2 (Pins 26, 17): Switch Node Connections to
Inductors. Voltage swing at these pins is from a Schottky
diode (external) voltage drop below ground to V
TG1, TG2 (Pins 27, 16): High Current Gate Drives for Top
N-Channel MOSFETs. These are the outputs of floating
drivers with a voltage swing equal to INTV
superimposed on the switch node voltage SW.
IN
(Pin 24): Main Supply Pin. A bypass capacitor should
CC
OUT
CC
CC
(Pin 21): Output of the Internal 5V Linear Low
connection in Applications section. Do not exceed
(Pin 22): External Power Input to an Internal
(Pin 10): Output of a linear regulator capable of
CC
power, bypassing the internal low dropout
CC
CC
. This switch closes and
CC
is higher than 4.7V. See
CC
to (V
Switch. The driver and
CC
pins. Voltage swing
IN
+ INTV
CC
CC
.
CC
regulator
CC
IN
– 0.5V
.
).
OUT
IN
.