LTC3633 LINER [Linear Technology], LTC3633 Datasheet - Page 8

• Manufacturer Part Number: LTC3633
• Description: Dual Channel 3A, 15V Monolithic Synchronous Step-Down Regulator
• Manufacturer: LINER [Linear Technology]

PIN FUNCTIONS
LTC3633
PGOOD1 (Pin 1/Pin 4): Channel 1 Open-Drain Power
Good Output Pin. PGOOD1 is pulled to ground when the
voltage on the V
internal 0.6V reference. PGOOD1 becomes high imped-
ance once the V
the internal reference.
PHMODE (Pin 2/Pin 5): Phase Select Input. Tie this pin
to ground to force both channels to switch in phase. Tie
this pin to INTV
out of phase. Do not fl oat this pin.
RUN1 (Pin 3/Pin 6): Channel 1 Regulator Enable Pin.
Enables channel 1 operation by tying RUN above 1.22V.
Tying it below 1V places the part into shutdown. Do not
fl oat this pin.
MODE/SYNC (Pin 4/Pin 7): Mode Select and External
Synchronization Input. Tie this pin to ground to force
continuous synchronous operation at all output loads.
Floating this pin or tying it to INTV
Burst Mode operation at light loads. Drive this pin with a
clock to synchronize the LTC3633 switching. An internal
phase-locked loop will force the bottom power NMOS’s
turn on signal to be synchronized with the rising edge of
the CLKIN signal. When this pin is driven with a clock,
forced continuous mode is automatically selected.
RT (Pin 5/Pin 8): Oscillator Frequency Program Pin.
Connect an external resistor (between 80k to 640k) from
this pin to SGND in order to program the frequency from
500kHz to 4MHz. When RT is tied to INTV
frequency will default to 2MHz.
RUN2 (Pin 6/Pin 9): Channel 2 Regulator Enable Pin.
Enables channel 2 operation by tying RUN above 1.22V.
Tying it below 1V places the part into shutdown. Do not
fl oat this pin.
SGND (Pin 7/Pin 10): Signal Ground Pin. This pin should
have a low noise connection to reference ground. The
feedback resistor network, external compensation network,
and RT resistor should be connected to this ground.
PGOOD2 (Pin 8/Pin 11): Channel 2 Open-Drain Power
Good Output Pin. PGOOD2 is pulled to ground when the
voltage on the V
internal 0.6V reference. PGOOD2 becomes high imped-
8
CC
FB1
FB1
FB2
to force both channels to switch 180°
pin returns to within ±5% (typical) of
pin is not within ±8% (typical) of the
pin is not within 8% (typical) of the
(QFN/TSSOP)
CC
enables high effi ciency
CC
, the switching
ance once the V
the internal reference.
V
Pin. Input to the error amplifi er that compares the feedback
voltage to the internal 0.6V reference voltage. Connect this
pin to a resistor divider network to program the desired
output voltage.
TRACKSS2 (Pin 10/Pin 13): Output Tracking and Soft-Start
Input Pin for Channel 2. Forcing a voltage below 0.6V on
this pin bypasses the internal reference input to the error
amplifi er. The LTC3633 will servo the FB pin to the TRACK
voltage under this condition. Above 0.6V, the tracking func-
tion stops and the internal reference resumes control of
the error amplifi er. An internal 1.4μA pull up current from
INTV
connecting a capacitor between this pin and SGND.
ITH2 (Pin 11/Pin 14): Channel 2 Error Amplifi er Output
and Switching Regulator Compensation Pin. Connect this
pin to appropriate external components to compensate
the regulator loop frequency response. Connect this pin
to INTV
V
nel 2. This pin sets the voltage trip point for the on-time
comparator. Tying this pin to the output voltage makes
the on-time proportional to V
V
than the set frequency. The pin impedance is nominally
180kΩ.
SW2 (Pins 13, 14/Pins 16, 17): Channel 2 Switch Node
Connection to External Inductor. Voltage swing of SW is
from a diode voltage drop below ground to V
V
Channel 2. Input voltage to the on chip power MOSFETs
on channel 2. This input is capable of operating from a
different supply voltage than V
BOOST2 (Pin 17/Pin 20): Boosted Floating Driver Supply
for Channel 2. The (+) terminal of the bootstrap capacitor
connects to this pin while the (–) terminal connects to
the SW pin. The normal operation voltage swing of this
pin ranges from a diode voltage drop below INTV
to V
FB2
ON2
OUT2
IN2
IN
CC
(Pins 15, 16/Pins 18, 19): Power Supply Input for
(Pin 9/Pin 12): Channel 2 Output Feedback Voltage
(Pin 12/Pin 15): On-Time Voltage Input for Chan-
+INTV
> 6V, switching frequency may become higher
CC
allows a soft start function to be implemented by
to use the default internal compensation.
CC
.
FB2
pin returns to within ±5% (typical) of
OUT2
IN1
.
when V
OUT2
IN
< 6V. When
.
CC
3633f
up