LTC3822 datasheet(6/20 Pages) LINER

6 / 20 page

LTC3822

3822f

PI FU CTIO S

BG (Pin 1): Bottom Gate Driver Output. This pin drives the

gate of the external bottom MOSFET. This pin has an

output swing from GND to BOOST.

TG (Pin 2): Top Gate Driver Output. This pin drives the gate

of the external topside MOSFET. This pin has an output

swing from GND to BOOST.

BOOST (Pin 3): Positive Supply Pin for the Gate Driver

Circuitry. A bootstrapped capacitor, charged through an

external Schottky diode from VIN, is connected between

the BOOST and SW pins. Voltage swing at the BOOST pin

is from VINto2VIN.Alternatively,thediodecanbeconnected

to SW and a separate 5V supply to provide 5V gate drive.

In this case, the BOOST pin swings from 5V to 5V + VIN.

VIN (Pin 4): This pin powers the control circuitry and

serves as the positive input to the differential current

comparator. Pin 4 must not be locally decoupled with a

capacitor as it is also the positive terminal for

current sense.

SW (Pin 5): Switch Node Connection to Inductor. This pin

is also the negative input to the differential current

comparator and an input to the reverse current comparator.

Normally this pin is connected to the source of the external

top-side MOSFET, the drain of the external bottom-side

MOSFET, and the inductor.

FREQ (Pin 6): This pin serves as the frequency select

input. Tying this pin to GND selects 300kHz operation;

tying this pin to VIN selects 750kHz operation. Floating this

pin selects 550kHz operation.

IPRG (Pin 7): Selects maximum peak sense voltage

between the VIN and SW pins (i.e., the maximum allowed

drop across the external top-side MOSFET). Tie to

VIN, GND or float to select 200mV, 82mV or 120mV

respectively.

VFB (Pin 8): Feedback Pin. This pin receives the remotely

sensed feedback voltage from an external resistor divider

across the output.

ITH (Pin 9): Current Threshold and Error Amplifier

Compensation Point. Nominal operating range on this pin

is from 0.7V to 2V. The voltage on this pin determines the

threshold of the main current comparator.

RUN (Pin 10): Run Control Input. Forcing this pin below

1.1V shuts down the chip. Driving this pin to VIN or

releasing this pin enables the chip to start-up with the

internal soft-start.

GND (Pin 11): Exposed Pad. The exposed pad is ground

and must be soldered to the PCB ground for electrical

contact and optimal thermal performance.

LTC3822 Datasheet(PDF) 6 Page - Linear Technology

LTC3822 Datasheet(HTML) 6 Page - Linear Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Datasheet Download

Link URL