LTC3446 Datasheet, PDF(8/20 Page) Linear Technology – Monolithic Buck Regulator with Dual VLDO Regulators

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LTC3446 Datasheet, PDF (8/20 Pages) Linear Technology – Monolithic Buck Regulator with Dual VLDO Regulators

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LTC3446

PIN FUNCTIONS

MODESEL (Pin 1): Chooses Between Burst Mode Operation

and Pulse Skipping Operation at Light Loads. Forcing this

pin below 0.3V allows the buck converter to automatically

enter Burst Mode operation at light loads. Forcing this pin

above 1V disallows entering Burst Mode operation; the

buck converter will cycle skip at light loads. Do not leave

this pin ï¬oating. This is a MOS gate input.

VIN (Pin 2): Input Supply to the LTC3446. Must be

closely decoupled to GND with a 10Î¼F or greater ceramic

capacitor.

ITH (Pin 3): Buck Error Ampliï¬er Output and Servo-Loop

Compensation Point.

PGOOD (Pin 4): Supply Monitor Output, Open-Drain

NMOS.

LVOUT1 (Pin 5): Output of the First VLDO Regulator.

LVIN (Pin 6): Input Supply to the LTC3446âs VLDO Circuits.

Bypass LVIN to GND with at least a 1Î¼F low ESR ceramic

capacitor. Typical LTC3446 application circuits will connect

this pin to the output of the buck converter but this is not

required. The VLDO regulators may be used independently

of the buck converter.

LVOUT2 (Pin 7): Output of the Second VLDO Regulator.

LVFB2 (Pin 9): Feedback Pin for the Second VLDO Regulator.

An output divider should be connected from LVOUT2 to LVFB2

to set the desired LVOUT2 regulated output voltage.

LVFB1 (Pin 10): Feedback Pin for the First VLDO Regulator.

An output divider should be connected from LVOUT1 to LVFB1

to set the desired LVOUT1 regulated output voltage.

ENLDO1/ENLDO2 (Pin 11/Pin 8): Enable Pin for the First

and Second VLDO Regulators, Respectively. Forcing this

pin above 1V enables the corresponding VLDO regulator

and forcing this pin below 0.3V shuts it down. Each VLDO

regulator draws <1Î¼A of supply current in shutdown. Do

not leave this pin ï¬oating. This is a MOS gate input.

BUCKFB (Pin 12): Buck Converterâs Feedback Pin. Receives

the feedback voltage from an external resistive divider

across the output. External resistance from this pin to

ground should be equal to or less than 50k.

ENBUCK (Pin 13): Enable Pin for the LTC3446âs Buck

Converter Circuit. Forcing this pin above 1V enables the

buck converter and forcing this pin below 0.3V shuts down

the converter. In shutdown, the buck converter draws <1Î¼A

of supply current. Do not leave this pin ï¬oating. This is a

MOS gate input.

SW (Pin 14): Switch Node Connection to Inductor. This

pin connects to the drains of the internal main and syn-

chronous power MOSFET switches.

Exposed Pad (Pin 15): Ground. The Exposed Pad is the

only ground and must connect to the PCB ground for

electrical contact and rated thermal performance.

3446fd

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