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LT3740

3740fc

Error Ampliﬁer Transconductance

vs Temperature

BIAS-VIN to Enable Controller

vs Temperature

Undervoltage Lockout Threshold

vs Temperature

PIN FUNCTIONS

SN– (Pin 1): Negative Current Sensing Pin. Connect this

pin to the source of the bottom MOSFET for No RSENSE

or to a current sense resistor.

PGND (Pin 2): Power Ground. Connect this pin closely to

the source of the bottom N-channel MOSFET.

BGATE (Pin 3): Bottom Gate Drive. Drives the gate of the

bottom N-channel MOSFET.

BGDP (Pin 4): Bottom Gate Drive Power Supply. Connect

this pin to a voltage source higher than 7V (VIN or BIAS).

SN+ (Pin 5):

Positive Current Sensing Pin. Connect this

pin to the drain of the bottom MOSFET for No RSENSE or

to a current sense resistor.

SW (Pin 6): Switch Node. Connect this pin to the source

of the top N-channel MOSFET and the drain of the bottom

N-channel MOSFET.

TGATE (Pin 7): Top Gate Drive. Drives the gate of the top

N-channel MOSFET to BIAS.

BIAS (Pin 8): Top Gate Drive Power Supply. Connect a

capacitor between this pin and VIN.

SWB (Pin 9): Switch Pin of the Internal Boost. Connect

the boost inductor here.

VIN (Pin 10): Input Supply Pin. Must be locally bypassed

with a capacitor.

RANGE (Pin 11): Current Limit Range Select Pin. Ground

this pin for 50mV current sense voltage limit. Leave this

pin open for 80mV current sense voltage limit. Connect

this pin to VIN for current sense voltage limit of 105mV.

PGOOD (Pin 12): Power Good Output. Open collector

logic output that is pulled low when the FB voltage lower

than 720mV.

SHDN(Pin13):ShutdownPin.Connectto2.5Vorhigherto

enable device; 0.5V or less to disable device. Also, this pin

functions as soft-start when a voltage ramp is applied.

XREF (Pin 14): External Reference Pin. This pin sets the

FB voltage externally between 0V and 0.8V. It can be used

to slave the output voltage during normal operation or the

output start-up behavior to an external signal source. Tie

this pin to 1V or higher to use the internal 0.8V reference.

FB (Pin 15): Feedback Pin. Pin voltage is regulated to 0.8V

if internal reference is used or to the XREF pin if voltage

is between 0V and 0.8V. Connect the feedback resistor

divider to this pin.

TEMPERATURE (°C)

–50

340

390

370

380

350

360

400

3740 G12

330

320

310

300

–25

100

TEMPERATURE (°C)

–50

7.20

7.45

7.35

7.40

7.25

7.30

7.50

3740 G13

7.15

7.10

7.05

7.00

–25

100

TEMPERATURE (°C)

–50

2.0

2.5

1.5

3.0

3740 G14

1.0

0.5

–25

100

TYPICAL PERFORMANCE CHARACTERISTICS (T

A = 25°C, unless otherwise noted)

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