LTC3608 LINER [Linear Technology], LTC3608 Datasheet - Page 8

• Manufacturer Part Number: LTC3608
• Description: 18V, 8A Monolithic Synchronous Step-Down DC/DC Converter
• Manufacturer: LINER [Linear Technology]

PIN FUNCTIONS
LTC3608
PV
Main Input Supply. Decouple this pin to power PGND with
the input capacitance C
SW (Pins 8, 33, 41, 42, 43, 44, 45, 46, 47, 55): Switch
Node Connection to the Inductor. The (–) terminal of the
bootstrap capacitor C
from a diode voltage drop below ground up to V
SGND (Pins 10, 14, 15, 20, 26, 27, 54): Signal Ground. All
small-signal components and compensation components
should connect to this ground, which in turn connects to
PGND at one point.
BOOST (Pin 11): Boosted Floating Driver Supply. The
(+) terminal of the bootstrap capacitor C
This pin swings from a diode voltage drop below INTV
up to V
RUN/SS (Pin 12): 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
the on-time comparator. Tying this pin to the output volt-
age or an external resistive divider from the output makes
the on-time proportional to V
defaults to 0.7V when the pin is grounded and defaults to
2.4V when the pin is tied to INTV
in high V
PGOOD (Pin 16): 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 adjusts maximum valley current and can be set
from 0.5V to 0.7V by a resistive divider from INTV
defaults to 0.7V if the V
results in a typical 19A current limit.
8
ON
RNG
IN
(Pin 13): On-Time Voltage Input. Voltage trip point for
(Pins 1, 2, 3, 4, 5, 6, 7, 48, 49, 50, 51, 52, 53):
(Pin 17): Current Limit Range Input. The voltage at
IN
OUT
+ INTV
applications to use a lower R
CC
.
B
also connects here. This pin swings
IN
RNG
pin is tied to ground which
OUT
CC
. The comparator input
. Tie this pin to INTV
B
connects here.
ON
value.
IN
.
CC
. It
CC
CC
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).
FCB (Pin 19): Forced Continuous Input. Tie this pin to
ground to force continuous synchronous operation at low
load, to INTV
low load or to a resistive divider from a secondary output
when using a secondary winding.
NC (Pins 9, 21, 24, 25, 28): No Connection.
I
to this pin to set the one-shot timer current and thereby
set the switching frequency.
V
connects the error amplifi er input to an external resistive
divider from V
EXTV
4.7V, an internal switch connects this pin to INTV
shuts down the internal regulator so that controller and
gate drive power is drawn from EXTV
7V at this pin and ensure that EXTV
SV
INTV
driver and control circuits are powered from this voltage.
Decouple this pin to power ground with a minimum of
4.7μF low ESR tantalum or ceramic capacitor.
PGND (Pins 34, 35, 36, 37, 38, 39, 40): Power Ground.
Connect this pin closely to the (–) terminal of C
the (–) terminal of C
TH
ON
FB
IN
(Pin 18): Current Control Threshold and Error Amplifi er
(Pin 22): On-Time Current Input. Tie a resistor from V
(Pin 23): Error Amplifi er Feedback Input. This pin
CC
(Pin 30): Supply pin for internal PWM controller.
CC
(Pin 29): External V
(Pins 31, 32): Internal 5V Regulator Output. The
CC
OUT
to enable discontinuous mode operation at
.
IN
.
CC
Input. When EXTV
CC
CC
< V
. Do not exceed
IN
.
CC
exceeds
VCC
CC
3608fa
and
and
IN