LTC3714 Linear, LTC3714 Datasheet - Page 8

• Manufacturer Part Number: LTC3714
• Description: Wide Operating Range / Step-Down Controller with Internal Op Amp
• Manufacturer: Linear

PI FU CTIO S
BG (Pin 1): Bottom Gate Drive. Drives the gate of the
bottom N-channel MOSFET between ground and INTV
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 C
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
voltage drop below ground up to V
TG (Pin 5): Top Gate Drive. Drives the top N-channel
MOSFET with a voltage swing equal to INTV
posed on the switch node voltage SW.
BOOST (Pin 6): Boosted Floating Driver Supply. The (+)
terminal of the bootstrap capacitor C
pin swings from a diode voltage drop below INTV
V
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 2.5 A 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/ F) and the time delay
for overcurrent latchoff (see Applications Information).
Forcing this pin below 0.8V shuts down the device.
V
the on-time comparator. Tying this pin to the output
voltage makes the on-time proportional to V
comparator input defaults to 0.7V when the pin is grounded,
2.4V when the pin is tied to INTV
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
this pin is ten times the nominal sense voltage at maxi-
LTC3714
8
IN
ON
RNG
U
+ INTV
(Pin 11): On-Time Voltage Input. Voltage trip point for
(Pin 13): Sense Voltage Range Input. The voltage at
CC
U
B
connects here. This pin swings from a diode
.
VCC
and the (–) terminal of C
U
CC
IN
.
B
.
connects here. This
CC
IN
.
superim-
OUT
CC
. The
up to
CC
.
mum output current and can be set from 0.5V to 2V by a
resistive divider from INTV
to 70mV when this pin is tied to ground, 140mV when tied
to INTV
I
fier Compensation Point. The current comparator thresh-
old increases with this control voltage. The voltage ranges
from 0V to 2.4V with 0.8V corresponding to zero sense
voltage (zero current).
OPV
INTV
OP
OP
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
at low load or to a resistive divider from a secondary output
when using a secondary winding.
I
V
set the switching frequency.
V
connects 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
voltage connects here to the input of the internal resistive
feedback divider.
EXTV
ceeds 4.7V, an internal switch connects this pin to INTV
and shuts down the internal regulator so that controller
and gate drive power is drawn from EXTV
7V at this pin and ensure that EXTV
V
SGND with an RC filter (1 , 0.1 F).
TH
ON
IN
FB
OSENSE
IN
–
+
(Pin 14): Current Control Threshold and Error Ampli-
to this pin to set the one-shot timer current and thereby
(Pin 21): On-Time Current Input. Tie a resistor from
(Pin 27): Main Input Supply. Decouple this pin to
IN
(Pin 22): Error Amplifier Feedback Input. This pin
CC
(Pin 16): Negative Input of the Internal Op Amp.
(Pin 17): Positive Input of the Internal Op Amp.
CC
(Pin 15): Internal Op Amp Supply. Connect to
CC
or a separate supply greater than 5V.
(Pin 26): External V
(Pin 23): Output Voltage Sense. The output
.
CC
to enable discontinuous mode operation
CC
CC
. The sense voltage defaults
Input. When EXTV
CC
< V
CC
. Do not exceed
IN
.
CC
ex-
3714f
CC