8
LTC1929/LTC1929-PG
RUN/SS (Pin 1): Combination of Soft-Start, Run Control
Input and Short-Circuit Detection Timer. A capacitor to
ground at this pin sets the ramp time to full current output.
Forcing this pin below 0.8V causes the IC to shut down all
internal circuitry. All functions are disabled in shutdown.
SENSE1
+
, SENSE2
+
(Pins 2,14): The (+) Input to the
Differential Current Comparators. The I
TH
pin voltage and
built-in offsets between SENSE
–
and SENSE
+
pins in
conjunction with R
SENSE
set the current trip threshold.
SENSE1
–
, SENSE2
–
(Pins 3, 13): The (–) Input to the
Differential Current Comparators.
EAIN (Pin 4): Input to the Error Amplifier that compares
the feedback voltage to the internal 0.8V reference voltage.
This pin is normally connected to a resistive divider from
the output of the differential amplifier (DIFFOUT).
PLLFLTR (Pin 5): The Phase-Locked Loop’s Low Pass
Filter is tied to this pin. Alternatively, this pin can be driven
with an AC or DC voltage source to vary the frequency of
the internal oscillator.
PLLIN (Pin 6): External Synchronization Input to Phase
Detector. This pin is internally terminated to SGND with
50kΩ. The phase-locked loop will force the rising top gate
signal of controller 1 to be synchronized with the rising
edge of the PLLIN signal.
NC (Pins 7, 28): Not connected.
I
TH
(Pin 8): Error Amplifier Output and Switching Regula-
tor Compensation Point. Both current comparator’s thresh-
olds increase with this control voltage. The normal voltage
range of this pin is from 0V to 2.4V
SGND (Pin 9): Signal Ground, common to both control-
lers, must be routed separately from the input switched
current ground path to the common (–) terminal(s) of the
C
OUT
capacitor(s).
V
DIFFOUT
(Pin 10): Output of a Differential Amplifier that
provides true remote output voltage sensing. This pin
normally drives an external resistive divider that sets the
output voltage.
V
OS
–
, V
OS
+
(Pins 11, 12): Inputs to an Operational
Amplifier. Internal precision resistors capable of being
electronically switched in or out can configure it as a
PI FU CTIO S
UUU
differential amplifier (default for the LTC1929-PG) or an
uncommitted Op Amp.
AMPMD (Pin 15): (LTC1929 Only) This Logic Input pin
controls the connections of internal precision resistors
that configure the operational amplifier as a unity-gain
differential amplifier.
PGOOD (Pin 15): (LTC1929-PG Only) Open-Drain Logic
Output. PGOOD is pulled to ground when the voltage on
the EAIN pin is not within ±7.5% of its set point.
TG2, TG1 (Pins 16, 27): High Current Gate Drives for Top
N-Channel MOSFETS. These are the outputs of floating
drivers with a voltage swing equal to INTV
CC
superim-
posed on the switch node voltage SW.
SW2, SW1 (Pins 17, 26): Switch Node Connections to
Inductors. Voltage swing at these pins is from a Schottky
diode (external) voltage drop below ground to V
IN
.
BOOST2, BOOST1 (Pins 18, 25): Bootstrapped Supplies
to the Topside Floating Drivers. Capacitors are connected
between the Boost and Switch pins, and Schottky diodes
are tied between the Boost and INTV
CC
pins.
BG2, BG1 (Pins 19, 23): Voltage Swing High Current Gate
Drives for Bottom Synchronous N-Channel MOSFETS.
Voltage swing at these pins is from ground to INTV
CC
.
PGND (Pin 20): Driver Power Ground. Connects to sources
of bottom N-channel MOSFETS and the (–) terminals of
C
IN
.
INTV
CC
(Pin 21): Output of the Internal 5V Linear Low
Dropout Regulator and the EXTV
CC
Switch. The driver and
control circuits are powered from this voltage source.
Decouple to power ground with a 1µF ceramic capacitor
placed directly adjacent to the IC and minimum of 4.7µF
additional tantalum or other low ESR capacitor.
EXTV
CC
(Pin 22): External Power Input to an Internal
Switch . This switch closes and supplies INTV
CC,
bypass-
ing the internal
low dropout regulator whenever EXTV
CC
is
higher than 4.7V. See EXTV
CC
Connection in the Applica-
tions Information section. Do not exceed 7V on this pin
and ensure V
EXTVCC
≤ V
IN
.
V
IN
(Pin 24): Main Supply Pin. Should be closely decoupled
to the IC’s signal ground pin.
