LT3742EUF-TRPBF 查看數據表（PDF） - Linear Technology

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LT3742EUF-TRPBF

Dual, 2-Phase Step-Down Switching Controller

Linear Technology 

LT3742

Pin Functions

G1, G2 (Pins 1, 6): Gate Drives. These pins provide high

current gate drive for the external N-channel MOSFETs.

These pins are the outputs of floating drivers whose volt-

age swings between the BIAS and SW pins.

VIN (Pin 2): Input Voltage. This pin supplies current to the

internal circuitry of the LT3742. This pin must be locally

bypassed with a capacitor.

UVLO (Pin 3): Undervoltage Lockout. Do not leave this

pin open ; connect it to VIN if not used. A resistor divider

connected to VIN is tied to this pin to program the mini-

mum input voltage at which the LT3742 will operate. When

this pin is less than 1.25V, the controllers are disabled

(the RUN/SS pins are still used to turn on each switching

regulator). Once this pin drops below 1.25V, a 3µA current

sink draws current into the pin to provide programmable

hysteresis for UVLO.

BIAS (Pin 4): Bias for Gate Drive. This pin provides a bias

voltage higher than the input voltage to drive the external

N-channel MOSFETs. The voltage on this pin is regulated

to VIN + 7V.

SWB (Pin 5): Bias Regulator Switch. This is the collec-

tor of an internal NPN switch used to generate the bias

voltage to provide gate drive for the external N-channel

MOSFETs.

RUN/SS1, RUN/SS2 (Pins 16, 15): Run/Soft-Start Pins.

These pins are used to shut down each controller. They

also provide a soft-start function with the addition of an

external capacitor. To shut down any regulator, pull the

RUN/SS pin to ground with an open-drain or open-col-

lector device. If neither feature is used, leave these pins

unconnected.

PG1, PG2 (Pins 17, 14): Power Good. These pins are

open-collector outputs of internal comparators. PG remains

low until the FB pin is within 90% of the final regulation

voltage. As well as indicating output regulation, the PG

pins can be used to sequence the switching regulators.

The PG outputs are valid when VIN is greater than 4V

and either of the RUN/SS pins is high. The power good

comparators are disabled in shutdown. If not used, these

pins should be left unconnected.

VC1, VC2 (Pins 18, 13): Control Voltage and Compensation

Pins for Internal Error Amplifiers. Connect a series RC

from these pins to ground to compensate each switching

regulator loop.

FB1, FB2 (Pins 19, 12): Feedback Pins. The LT3742

regulates these pins to 800mV. Connect the feedback

resistors to this pin to set the output voltage for each

switching regulator.

SENSE1–, SENSE2– (Pins 20, 11): Negative Current Sense

Inputs. These pins (along with the SENSE+ pins) are used to

sense the inductor current for each switching regulator.

SENSE1+, SENSE2+ (Pins 21, 10): Positive Current Sense

Inputs. These pins (along with the SENSE– pins) are used to

sense the inductor current for each switching regulator.

SW1, SW2 (Pins 24, 7): Switch Nodes. These pins connect

to the source of the external N-channel MOSFETs and to

the external inductors and diodes.

Exposed Pad (Pin 25): Ground. The Exposed Pad of the

package provides both electrical contact to ground and

good thermal contact to the printed circuit board. The

Exposed Pad must be soldered to the circuit board to

ensure proper operation.

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