LTC3714_15 Datasheet, PDF (8/28 Pages) Linear Technology – Intel Compatible, Wide Operating Range, Step-Down Controller with Internal Op Amp

LTC3714
Pin Functions
BG (Pin 1): Bottom Gate Drive. Drives the gate of the
bottom N-channel MOSFET between ground and INTV_CC.
PGND (Pin 2): Power Ground. Connect this pin closely to
the bottom of the sense resistor or if no sense resistor is
used, to the source of the bottom N-channel MOSFET, the
(–) terminal of CV_CC and the (–) terminal of C_IN.
SENSE (Pin 3): Current Sense Comparator Input. The (+)
input to the current comparator is normally connected to
the SW node unless using a sense resistor (see Applica-
tions Information).
SW (Pin 4): Switch Node. The (–) terminal of the bootstrap
capacitor C_B connects here. This pin swings from a diode
voltage drop below ground up to V_IN.
TG (Pin 5): Top Gate Drive. Drives the top N-channel
MOSFET with a voltage swing equal to INTV_CC superim-
posed on the switch node voltage SW.
BOOST (Pin 6): Boosted Floating Driver Supply. The (+)
terminal of the bootstrap capacitor C_B connects here. This
pin swings from a diode voltage drop below INTV_CC up
to V_IN + INTV_CC.
VID0-VID4 (Pins 7, 8, 9, 24, 25): VID Digital Inputs. The
voltage identification (VID) code sets the internal feedback
resistor divider ratio for different output voltages as shown
in Table 1. If unconnected, the pins are pulled high by
internal 2.5µA current sources.
RUN/SS (Pin 10): Run Control and Soft-Start Input. A
capacitor to ground at this pin sets the ramp time to full
output current (approximately 3s/µF) and the time delay
for overcurrent latchoff (see Applications Information).
Forcing this pin below 0.8V shuts down the device.
V_ON (Pin 11): On-Time Voltage Input. Voltage trip point for
the on-time comparator. Tying this pin to the output voltage
makes the on-time proportional to V_OUT. The comparator
input defaults to 0.7V when the pin is grounded, 2.4V when
the pin is tied to INTV_CC.
PGOOD (Pin 12): Power Good Output. Open drain logic
output that is pulled to ground when the output voltage
is not within ±10% of the regulation point.
V_RNG (Pin 13): Sense Voltage Range Input. The voltage
at this pin is ten times the nominal sense voltage at maxi-
8
mum output current and can be set from 0.5V to 2V by a
resistive divider from INTV_CC. The sense voltage defaults
to 70mV when this pin is tied to ground, 140mV when
tied to INTV_CC.
ITH (Pin 14): Current Control Threshold and Error Amplifier
Compensation Point. The current comparator threshold
increases with this control voltage. The voltage ranges
from 0V to 2.4V with 0.8V corresponding to zero sense
voltage (zero current).
OPV_IN (Pin 15): Internal Op Amp Supply. Connect to
INTV_CC or a separate supply greater than 5V.
OP^– (Pin 16): Negative Input of the Internal Op Amp.
OP⁺ (Pin 17): Positive Input of the Internal Op Amp.
OPOUT (Pin 18): Output of the Internal Op Amp.
SGND (Pin 19): Signal Ground. All small-signal compo-
nents and compensation components should connect to
this ground, which in turn connects to PGND at one point.
FCB (Pin 20): Forced Continous Input. Tie this pin to
ground to force continuous synchronous operation at low
load, to INTV_CC to enable discontinuous mode operation at
low load or to a resistive divider from a secondary output
when using a secondary winding.
I_ON (Pin 21): On-Time Current Input. Tie a resistor from V_IN
to this pin to set the one-shot timer current and thereby
set the switching frequency.
V_FB (Pin 22): Error Amplifier Feedback Input. This pin con-
nects to both the error amplifier input and to the output
of the internal resistive divider. It can be used to attach
additional compensation components if desired.
V_OSENSE (Pin 23): Output Voltage Sense. The output volt-
age connects here to the input of the internal resistive
feedback divider.
EXTV_CC (Pin 26): External V_CC Input. When EXTV_CC exceeds
4.7V, an internal switch connects this pin to INTV_CC and
shuts down the internal regulator so that controller and
gate drive power is drawn from EXTV_CC. Do not exceed
7V at this pin and ensure that EXTV_CC < V_IN.
V_IN (Pin 27): Main Input Supply. Decouple this pin to
SGND with an RC filter (1Ω, 0.1µF).
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