LTC1929 LINER [Linear Technology], LTC1929 Datasheet - Page 4

• Manufacturer Part Number: LTC1929
• Description: 2-Phase, High Efficiency, Synchronous Step-Down Switching Regulator
• Manufacturer: LINER [Linear Technology]

ELECTRICAL CHARACTERISTICS
PI FU CTIO S
LTC1929
Note 1: Absolute Maximum Ratings are those values beyond which the
life of a device may be impaired.
Note 2: T
dissipation P
LTC1929CG: T
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
Differential Current Comparators. The I
built-in offsets between SENSE
conjunction with R
SENSE1
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
50k . 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
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
4
TH
U
(Pin 8): Error Amplifier Output and Switching Regula-
J
is calculated from the ambient temperature T
+
–
, SENSE2
, SENSE2
D
U
J
according to the following formulas:
= T
A
+ (P
SENSE
D
–
+
• 95 C/W)
U
(Pins 3, 13): The (–) Input to the
(Pins 2,14): The (+) Input to the
set the current trip threshold.
–
and SENSE
TH
pin voltage and
A
and power
+
pins in
Note 3: The LTC1929 is tested in a feedback loop that servos V
specified voltage and measures the resultant V
Note 4: Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency. See Applications Information.
Note 5: When the AMPMD pin is high, the IC pins are connected directly to
the internal op amp inputs. When the AMPMD pin is low, internal MOSFET
switches connect four 40k resistors around the op amp to create a
standard unity-gain differential amp.
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
V
provides true remote output voltage sensing. This pin
normally drives an external resistive divider that sets the
output voltage.
V
fier. Internal precision resistors capable of being elec-
tronically switched in or out can configure it as a differen-
tial amplifier or an uncommitted Op Amp.
AMPMD (Pin 15): This Logic Input pin controls the
connections of internal precision resistors that configure
the operational amplifier as a unity-gain differential ampli-
fier.
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
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
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
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
OUT
DIFFOUT
OS
–
, V
capacitor(s).
OS
(Pin 10): Output of a Differential Amplifier that
+
(Pins 11, 12): Inputs to an Operational Ampli-
EAIN
CC
.
pins.
CC
superim-
ITH
IN
to a
.
CC
.