LTC3370 datasheet(9/24 Pages) AD

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LTC3315A

Rev. A

For more information www.analog.com

PIN FUNCTIONS

EN1 (Pin 1): Enable Input for Buck Regulator 1. Active

high. The EN1 pin has a precision threshold and an

optional external resistor divider from VIN or another

supply programs when Buck Regulator 1 is enabled. If

the precision threshold is not required, drive EN1 to VIN

to enable. Do not float.

FB1 (Pin 2): Feedback Input for Buck Regulator 1.

Program the output voltage and close the control loop

by connecting this pin to the middle node of a resistor

divider between the output and ground. The LTC3315A

regulates FB1 to 500mV (typical). A phase lead capaci-

tor connected between VOUT1 and FB1 may be used to

optimize transient response.

FB2 (Pin 3): Feedback Input for Buck Regulator 2.

Program the output voltage and close the control loop

by connecting this pin to the middle node of a resistor

divider between the output and ground. The LTC3315A

regulates FB2 to 500mV (typical). A phase lead capaci-

tor connected between VOUT2 and FB2 may be used to

optimize transient response.

EN2 (Pin 4): Enable Input for Buck Regulator 2. Active

high. The EN2 pin has a precision threshold and an

optional external resistor divider from VIN or another

supply programs when Buck Regulator 2 is enabled. If

the precision threshold is not required, drive EN2 to VIN

to enable. Do not float.

PGOOD (Pin 5): Power Good Output. Open drain out-

put. When the regulated output voltage of either enabled

switching regulator falls below its PGOOD threshold or

rises above its overvoltage threshold, this pin is driven

low. When both buck regulators are disabled PGOOD is

driven low.

SW2 (Pin 6): Switch Node for Buck Regulator 2. Connect

an inductor to this pin with a short, wide trace.

VIN (Pin 7, Pin 10): Input Supply Pins. The VIN pins sup-

ply current to internal circuitry and to each buck’s PMOS

power switch. Connect both VIN pins together with a short,

wide trace and bypass to GND with low ESR capacitors

located as close as possible to the pins.

GND (Pin 8, Pin 9, Exposed Pad Pin 13): Ground.

Connect the exposed pad to a continuous ground plane

on the printed circuit board directly under the LTC3315A

for electrical contact and rated thermal performance.

Additionally, Pin 8 and Pin 9 should be shorted to the

exposed pad with a wide trace.

SW1 (Pin 11): Switch Node for Buck Regulator 1. Connect

an inductor to this pin with a short, wide trace.

MODE/SYNC (Pin 12): Mode Selection and External Clock

Synchronization Input. Ground this pin to enable pulse-

skipping mode. For higher efficiency at light loads, tie

this pin to VIN to enable Burst Mode. For fast transient

response and constant frequency operation over a wide

load range, float this pin to enable forced continuous

mode. Drive MODE/SYNC with an external clock to syn-

chronize both buck converters to the applied frequency.

When syncing, the operating mode is forced continuous.

The slope compensation is automatically adapted to the

external clock frequency. In the absence of an external

clock both buck converters will switch at the default

switching frequency.

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