LTC3713 datasheet(7/24 Pages) LINER

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LTC3713

3713fa

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/

µF) and the time delay

for overcurrent latchoff (see Applications Information).

Forcing this pin below 0.8V shuts down the device.

VON (Pin 2): 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 VOUT. The

comparator input defaults to 0.7V when the pin is grounded,

2.4V when the pin is tied to INTVCC.

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.

VRNG (Pin 4): Sense Voltage Range Input. The voltage at

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 INTVCC. The nominal sense voltage

defaults to 70mV when this pin is tied to ground, 140mV

when tied to INTVCC.

FCB (Pin 5): Forced Continuous Input. Tie this pin to

ground to force continuous synchronous operation at low

load, to INTVCC to enable discontinuous mode operation

at low load or to a resistive divider from a secondary output

when using a secondary winding.

ITH (Pin 6): 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).

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.

ION (Pin 8): On-Time Current Input. Tie a resistor from VIN

to this pin to set the one-shot timer current and thereby set

the switching frequency.

VFB1 (Pin 9): Error Amplifier Feedback Input. This pin

connects the error amplifier input to an external resistive

divider from VOUT.

SHDN (Pin 10): Shutdown, Active Low. Tie to 1V or more

to enable boost converter portion of the LTC3713. Ground

to shut down.

VFB2 (Pin 12): Boost Converter Feedback. The VFB2 pin is

connected to INTVCC through a resistor divider to set the

voltage on INTVCC. Set INTVCC voltage according to:

VINTVCC = 1.23V(1 + RF4/RF3)

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 CVCC and the (–) terminal of CIN.

VIN2 (Pin 15): Input Supply Pin for Boost Converter

Portion of LTC3713. Must be locally bypassed.

VIN1 (Pin 16): Main Input Supply. Decouple this pin to

PGND with an RC filter (1

Ω, 0.1µF).

INTVCC (Pin 17): Internal Regulator Output. The driver and

control circuits are powered from this voltage. Decouple

this pin to power ground with a minimum of 4.7

µFlowESR

tantalum or ceramic capacitor.

BG (Pin 18): Bottom Gate Drive. Drives the gate of the

bottom N-channel MOSFET between ground and INTVCC.

SENSE– (Pin 20): Negative Current Sense Comparator

Input. The (–) input to the current comparator is normally

connected to power ground unless using a resistive di-

vider from INTVCC (see Applications Information).

SENSE+ (Pin 21): Positive Current Sense Comparator

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 CB connects here. This pin swings

from a diode voltage drop below ground up to VIN.

TG (Pin 23): Top Gate Drive. Drives the top N-channel

MOSFET with a voltage swing equal to INTVCC superim-

posed on the switch node voltage SW1.

BOOST (Pin 24): Boosted Floating Driver Supply. The (+)

terminal of the bootstrap capacitor CB connects here. This

pin swings from a diode voltage drop below INTVCC up to

VIN + INTVCC.

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