ltc3713 Linear Technology Corporation, ltc3713 Datasheet - Page 7

• Manufacturer Part Number: ltc3713
• Description: Low Input Voltage, High Power, No Rsense Synchronous Buck Dc/dc Controller
• Manufacturer: Linear Technology Corporation

PI FU CTIO S
RUN/SS (Pin 1): 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 3): Power Good Output. Open-drain logic
output that is pulled to ground when the output voltage is
not within 7.5% of the regulation point.
V
this pin is ten times the nominal sense voltage at maxi-
mum output current and can be set from 0.5V to 2V by a
resistive divider from INTV
defaults to 70mV when this pin is tied to ground, 140mV
when tied to INTV
FCB (Pin 5): Forced Continuous 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
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).
SGND (Pins 7, 11): Signal Ground. All small-signal com-
ponents and compensation components should connect to
this ground, which in turn connects to PGND at one point.
I
to this pin to set the one-shot timer current and thereby set
the switching frequency.
V
connects the error amplifier input to an external resistive
divider from V
SHDN (Pin 10): Shutdown, Active Low. Tie to 1V or more
to enable boost converter portion of the LTC3713. Ground
to shut down.
TH
ON
ON
RNG
FB1
U
(Pin 6): Current Control Threshold and Error Amplifier
(Pin 8): On-Time Current Input. Tie a resistor from V
(Pin 2): On-Time Voltage Input. Voltage trip point for
(Pin 9): Error Amplifier Feedback Input. This pin
(Pin 4): Sense Voltage Range Input. The voltage at
U
CC
OUT
to enable discontinuous mode operation
.
CC
U
.
CC
. The nominal sense voltage
CC
.
OUT
. The
IN
V
connected to INTV
voltage on INTV
SW2 (Pin 13): Boost Converter Switch Pin. Connect
inductor/diode for boost converter portion here. Minimize
trace area at this pin to keep EMI down.
PGND (Pins 14, 19): Power Ground. Connect these pins
closely to the source of the bottom N-channel MOSFET,
the (–) terminal of C
V
Portion of LTC3713. Must be locally bypassed.
V
PGND with an RC filter (1 , 0.1 F).
INTV
control circuits are powered from this voltage. Decouple
this pin to power ground with a minimum of 4.7 F low ESR
tantalum or ceramic capacitor.
BG (Pin 18): Bottom Gate Drive. Drives the gate of the
bottom N-channel MOSFET between ground and INTV
SENSE
Input. The (–) input to the current comparator is normally
connected to power ground unless using a resistive di-
vider from INTV
SENSE
Input. The (+) input to the current comparator is normally
connected to the SW1 node unless using a sense resistor
(see Applications Information).
SW1 (Pin 22): Switch Node. The (–) terminal of the
bootstrap capacitor C
from a diode voltage drop below ground up to V
TG (Pin 23): Top Gate Drive. Drives the top N-channel
MOSFET with a voltage swing equal to INTV
posed on the switch node voltage SW1.
BOOST (Pin 24): Boosted Floating Driver Supply. The (+)
terminal of the bootstrap capacitor C
pin swings from a diode voltage drop below INTV
V
FB2
IN2
IN1
IN
V
+ INTV
INTVCC
CC
(Pin 12): Boost Converter Feedback. The V
(Pin 16): Main Input Supply. Decouple this pin to
(Pin 15): Input Supply Pin for Boost Converter
–
+
(Pin 17): Internal Regulator Output. The driver and
(Pin 20): Negative Current Sense Comparator
(Pin 21): Positive Current Sense Comparator
CC
= 1.23V(1 + R
.
CC
CC
. Set INTV
CC
(see Applications Information).
VCC
through a resistor divider to set the
B
connects here. This pin swings
and the (–) terminal of C
F4
/R
CC
F3
)
voltage according to:
B
connects here. This
LTC3713
CC
superim-
FB2
IN
CC
IN
.
.
pin is
up to
3713fa
7
CC
.