LTC1775 Ver la hoja de datos (PDF) - Linear Technology

Número de pieza

componentes Descripción

Fabricante

LTC1775

High Power No RSENSE™ Current Mode Synchronous Step-Down Switching Regulator

Linear Technology 

LTC1775

PI FU CTIO S

EXTVCC (Pin 1): INTVCC Switch Input. When the EXTVCC

voltage is above 4.7V, the switch closes and supplies

INTVCC power from EXTVCC. Do not exceed 7V at this pin.

SYNC (Pin 2): Synchronization Input for Internal Oscilla-

tor. The oscillator will nominally run at 150kHz when open,

225kHz when tied above 1.2V, and will lock over a 1.5:1

clock frequency range.

RUN/SS (Pin 3): Run Control and Soft Start Input. A

capacitor to ground at this pin sets the ramp time to full

current output (approximately 1s/µF). Forcing this pin

below 1.4V shuts down the device.

FCB (Pin 4): Forced Continuous Input. Tie this pin to

ground to force synchronous operation at low load

currents, to a resistive divider from the secondary output

when using a secondary winding, or to INTVCC to enable

Burst Mode operation at low load currents.

ITH (Pin 5): Error Amplifier Compensation Point. The

current comparator threshold increases with this control

voltage, forcing inductor current to be roughly propor-

tional to VITH. Nominal voltage range for this pin is 0V to

2.4V.

SGND (Pin 6): Signal Ground. Connect to the (–) terminal

of COUT.

VOSENSE (Pin 7): Output Voltage Sense. Feedback input

from the remotely sensed output voltage or from an

external resistive divider across the output.

VPROG (Pin 8): Output Voltage Programming. When

VOSENSE is connected to the output, VPROG < 0.8V selects

a 3.3V output and VPROG > 3.5V selects a 5V output.

Leaving VPROG open allows the output voltage to be set by

an external resistive divider between the output and

VOSENSE.

PGND (Pin 9): Driver Power Ground. Connects to the

source of the bottom N-channel MOSFET, the (–) terminal

of CVCC and the (–) terminal of CIN.

BG (Pin 10): Bottom Gate Drive. Drives the gate of the

bottom N-channel MOSFET between ground and INTVCC.

INTVCC (Pin 11): Internal 5.2V Regulator Output. The

driver and control circuits are powered from this voltage.

Decouple this pin to power ground with a minimum of

4.7µF tantalum or other low ESR capacitor.

BOOST (Pin 12): Topside Floating Driver Supply. The (+)

terminal of the bootstrap capacitor connects here. This pin

swings from a Schottky diode drop below INTVCC to VIN +

INTVCC.

TG (Pin 13): Top Gate Drive. Drives the top N-channel

MOSFET with a voltage swing equal to INTVCC superim-

posed on the switch node voltage.

SW (Pin 14): Switch Node. The (–) terminal of the boot-

strap capacitor connects here. This pin swings from a

diode drop below ground up to VIN.

TK (Pin 15): Top MOSFET Kelvin Sense. MOSFET VDS

sensing requires this pin to be routed to the drain of the top

MOSFET separately from VIN.

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

ground with an RC filter (1Ω, 0.1µF) for applications

above 3A.

6

Share Link: