LTC3417 Datasheet, PDF (6/20 Pages) Linear Technology – Dual Synchronous 1.4A/800mA 4MHz Step-Down DC/DC Regulator

LTC3417
PI FU CTIO S (DFN/TSSOP)
RUN1 (Pin 1/Pin 2): Enable for 1.4A Regulator. When at
Logic 1, 1.4A regulator is running. When at 0V, 1.4A
regulator is off. When both RUN1 and RUN2 are at 0V, the
part is in shutdown.
V_IN1 (Pin 2/Pin 3): Supply Pin for P-Channel Switch of
1.4A Regulator.
I_TH1 (Pin 3/Pin 4): Error Amplifier Compensation Point for
1.4A Regulator. The current comparator threshold in-
creases with this control voltage. Nominal voltage range
for this pin is 0V to 1.5V.
V_FB1 (Pin 4/Pin 5): Receives the feedback voltage from
external resistive divider across the 1.4A regulator output.
Nominal voltage for this pin is 0.8V.
V_FB2 (Pin 5/Pin 6): Receives the feedback voltage from
external resistive divider across the 800mA regulator
output. Nominal voltage for this pin is 0.8V.
I_TH2 (Pin 6/Pin 7): Error Amplifier Compensation Point for
800mA regulator. The current comparator threshold in-
creases with this control voltage. Nominal voltage range
for this pin is 0V to 1.5V.
RUN2 (Pin 7/Pin 8): Enable for 800mA Regulator. When
at Logic 1, 800mA regulator is running. When at 0V,
800mA regulator is off. When both RUN1 and RUN2 are at
0V, the part is in shutdown.
V_IN2 (Pin 8/Pin 9): Supply Pin for P-Channel Switch of
800mA Regulator and Supply for Analog Circuitry.
MODE (Pin 9/Pin 12): Mode Selection Pin. This pin
controls the operation of the device. When the voltage on
the MODE pin is >(V_IN – 0.5V), Burst Mode operation is
selected. When the voltage on the MODE pin is <0.5V,
pulse skipping mode is selected. When the MODE pin is
held at V_IN/2, forced continuous mode is selected.
SW2 (Pin 10/Pin 13): Switch Node Connection to the
Inductor for the 800mA Regulator. This pin swings from
V_IN2 to PGND2.
PGOOD (Pin 11/Pin 14): Power Good Pin. This common
drain-logic output is pulled to GND when the output
voltage of either regulator is – 6% of regulation. If either
RUN1 or RUN2 is low (the respective regulator is in sleep
mode and therefore the output voltage is low), then
PGOOD reflects the regulation of the running regulator.
FREQ (Pin 12/Pin 15): Frequency Set Pin. When FREQ is
at V_IN, internal oscillator runs at 1.5MHz. When a resistor
is connected from this pin to ground, the internal oscillator
frequency can be varied from 0.6MHz to 4MHz.
GNDA (Pin 13/Pin 16): Analog Ground Pin for Internal
Analog Circuitry.
PHASE (Pin 14/Pin 17): Selects 800mA regulator switch-
ing phase with respect to 1.4A regulator switching. Set to
V_IN, the 1.4A regulator and the 800mA regulator are in
phase. When PHASE is at 0V, the 1.4A regulator and the
800mA regulator are switching 180 degrees out-of-phase.
SW1 (Pin 15/Pin 18): Switch Node Connection to the
Inductor for the 1.4A Regulator. This pin swings from V_IN1
to PGND1.
PGND1 (Pin 16/Pin 19): Ground for SW1 N-Channel
Driver.
PGND2, GNDD (Pins 1,10,11,20): TSSOP Package Only.
Ground for SW2 N-channel driver and digital ground for
circuit.
Exposed Pad (Pin 17/Pin 21): PGND2, GNDD. Ground for
SW2 N-channel driver and digital ground for circuit. The
Exposed Pad must be soldered to PCB ground.
3417fb
6