LTC3703IGN-5 Linear Technology, LTC3703IGN-5 Datasheet - Page 7

• Manufacturer Part Number: LTC3703IGN-5
• Description: IC,SMPS CONTROLLER,VOLTAGE-MODE,CMOS,SSOP,16PIN,PLASTIC
• Manufacturer: Linear Technology

PI FU CTIO S
MODE/SYNC (Pin 1/Pin 6): Pulse Skip Mode Enable/Sync
Pin. This multifunction pin provides Pulse Skip Mode
enable/disable control and an external clock input for
synchronization of the internal oscillator. Pulling this pin
below 0.8V or to an external logic-level synchronization
signal disables Pulse Skip Mode operation and forces
continuous operation. Pulling the pin above 0.8V enables
Pulse Skip Mode operation. This pin can also be connected
to a feedback resistor divider from a secondary winding on
the inductor to regulate a second output voltage.
f
this pin sets the free running frequency of the internal
oscillator. See applications section for resistor value se-
lection details.
COMP (Pin 3/Pin 8): Loop Compensation. This pin is
connected directly to the output of the internal error ampli-
fier. An RC network is used at the COMP pin to compensate
the feedback loop for optimal transient response.
FB (Pin 4/Pin 9): Feedback Input. Connect FB through a
resistor divider network to V
Also connect the loop compensation network from COMP
to FB.
I
the current limit comparator threshold. If the voltage drop
across the bottom MOSFET exceeds the magnitude of the
voltage at I
I
current threshold to be set with a single external resistor
to ground. See the Current Limit Programming section for
more information on choosing R
INV (Pin 6/Pin 11): Top/Bottom Gate Invert. Pulling this
pin above 2V sets the controller to operate in step-up
(boost) mode with the TG output driving the synchronous
MOSFET and the BG output driving the main switch. Below
1V, the controller will operate in step-down (buck) mode.
RUN/SS (Pin 7/Pin 13): Run/Soft-Start. Pulling RUN/SS
below 0.9V will shut down the LTC3703, turn off both of
the external MOSFET switches and reduce the quiescent
supply current to 50µA. A capacitor from RUN/SS to
ground will control the turn-on time and rate of rise of the
output voltage at power-up. An internal 4µA current source
pull-up at the RUN/SS pin sets the turn-on time at approxi-
mately 750ms/µF.
SET
MAX
MAX
U
(Pin 2/Pin 7): Frequency Set. A resistor connected to
pin has an internal 12µA current source, allowing the
(Pin 5/Pin 10): Current Limit Set. The I
U
MAX
, the controller goes into current limit. The
U
(GN16/G28)
OUT
to set the output voltage.
IMAX
.
MAX
pin sets
GND (Pin 8/Pin 14): Ground Pin.
BGRTN (Pin 9/Pin 15): Bottom Gate Return. This pin
connects to the source of the pull-down MOSFET in the BG
driver and is normally connected to ground. Connecting a
negative supply to this pin allows the synchronous
MOSFET’s gate to be pulled below ground to help prevent
false turn-on during high dV/dt transitions on the SW
node. See the Applications Information section for more
details.
BG (Pin 10/Pin 19): Bottom Gate Drive. The BG pin drives
the gate of the bottom N-channel synchronous switch
MOSFET. This pin swings from BGRTN to DRV
DRV
provides power to the BG output driver. This pin should be
connected to a voltage high enough to fully turn on the
external MOSFETs, normally 10V to 15V for standard
threshold MOSFETs. DRV
with a 10µF, low ESR (X5R or better) ceramic capacitor.
V
except the output drivers are powered from this pin. V
should be connected to a low noise power supply voltage
between 9V and 15V and should be bypassed to GND (pin
8) with at least a 0.1µF capacitor in close proximity to the
LTC3703.
SW (Pin 13/Pin 26): Switch Node Connection to Inductor and
Bootstrap Capacitor. Voltage swing at this pin is from a
Schottky diode (external) voltage drop below ground to V
TG (Pin 14/Pin 27): Top Gate Drive. The TG pin drives the
gate of the top N-channel synchronous switch MOSFET.
The TG driver draws power from the BOOST pin and
returns to the SW pin, providing true floating drive to the
top MOSFET.
BOOST (Pin 15/Pin 28): Top Gate Driver Supply. The
BOOST pin supplies power to the floating TG driver. The
BOOST pin should be bypassed to SW with a low ESR (X5R
or better) 0.1µF ceramic capacitor. An additional fast
recovery Schottky diode from DRV
a complete floating charge-pumped supply at BOOST.
V
connected to the high voltage input of the regulator and is
used by the internal feedforward compensation circuitry
to improve line regulation. This is not a supply pin.
CC
IN
(Pin 16/Pin 1): Input Voltage Sense Pin. This pin is
(Pin 12/Pin 21) : Main Supply Pin. All internal circuits
CC
(Pin 11/Pin 20): Driver Power Supply Pin. DRV
CC
should be bypassed to BGRTN
CC
to BOOST will create
LTC3703
CC
.
3703fa
7
IN
CC
CC
.