LTC3853_15 Datasheet, PDF (8/36 Pages) Linear Technology – Triple Output, Multiphase Synchronous Step-Down Controller

LTC3853
PIN FUNCTIONS
SENSE1⁺, SENSE2⁺, SENSE3⁺ (Pins 3, 5, 7): Current Sense
Comparator Inputs. The (+) inputs to the current compara-
tors are normally connected to DCR sensing networks or
current sensing resistors. SENSE3⁺ common modes up
to 13.5V, allowing higher V_OUT voltages on channel 3.
SENSE1^–, SENSE2^–, SENSE3^– (Pins 4, 6, 8): Current
Sense Comparator Inputs. The (–) inputs to the current
comparators are connected to the outputs. SENSE3^– com-
mon modes up to 13.5V, allowing higher V_OUT voltages
on channel 3.
V_FB1, V_FB2, V_FB3 (Pins 9, 12, 14): Error Amplifier Feedback
Inputs. These pins receive the remotely sensed feedback
voltages for each channel from external resistive dividers
across the outputs. Connecting V_FB2 to V_IN through a 200k
resistor enables dual output (2 + 1) mode.
I_TH1, I_TH2, I_TH3 (Pins 10, 13, 15): Current Control Thresh-
olds and Error Amplifier Compensation Points. Each as-
sociated channels’ current comparator tripping threshold
increases with its I_TH control voltage. In dual output
(2 + 1) mode, I_TH1 and I_TH2 need to be shorted externally.
SGND (Pin 11): Signal Ground. All small-signal compo-
nents and compensation components should connect to
this ground, which in turn connects to PGND at one point.
PGOOD3 (Pin 16): Power Good Indicator Output for Phase
3. Open-drain logic out that is pulled to ground when any
channel output exceeds the ±7.5% regulation window,
after the internal 17µs power bad mask timer expires.
PGOOD12 (Pin 17): Power Good Indicator Output for
Phases 1 and 2. Open-drain logic out that is pulled to
ground when any channel output exceeds the ±7.5%
regulation window, after the internal 17µs power bad
mask timer expires.
INTV_CC (Pin 22): Internal 5V Regulator Output. The
control circuits are powered from this voltage. Also
provides channel 3 driver power. Decouple this pin to
PGND with a minimum of 4.7µF low ESR tantalum or
ceramic capacitor.
EXTV_CC (Pin 23): External Power Input to an Internal Switch
Connected to INTV_CC. This switch closes and supplies the
IC power, bypassing the internal low dropout regulator,
whenever EXTV_CC is higher than 4.7V. Do not exceed 6V
on this pin and ensure V_IN > V_EXTVCC at all times.
V_IN (Pin 24): Main Input Supply. Decouple this pin to
PGND with a capacitor (0.1µF to 1µF).
DRV_CC12 (Pin 29): Driver Voltage Input for Channels 1 and
2. Do not exceed 6V on this pin. This pin must be tied to
INTV_CC externally.
BG1, BG2, BG3 (Pins 30, 28, 21): Bottom Gate Driver
Outputs. These pins drive the gates of the bottom N-
channel MOSFETs between PGND and INTV_CC/DRV_CC12.
SW1, SW2, SW3 (Pins 31, 27, 20): Switch Node Con-
nections to Inductors. Voltage swing at these pins is
from a Schottky diode (external) voltage drop below
ground to V_IN.
TG1, TG2, TG3 (Pins 32, 26, 19): Top Gate Driver Outputs.
These are the outputs of floating drivers with a voltage
swing equal to INTV_CC superimposed on the switch nodes
voltages.
BOOST1, BOOST2, BOOST3 (Pins 33, 25, 18): Boosted
Floating Driver Supplies. The (+) terminal of the boot-
strap capacitors connect to these pins. These pins swing
from a diode voltage drop below INTV_CC up to V_IN +
INTV_CC.
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