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LTC3113

3113f

PIN FUNCTIONS

VOUT (Pins 1, 2/Pins 2, 3): Buck-Boost Output Voltage. A

low ESR capacitor should be placed from VOUT to PGND.

The capacitor should be placed as close to the IC as pos-

sible and have a short return path to ground.

VIN (Pins 3, 4, 5/Pins 4, 5, 6): Power Input for the

Converter. A 47μF or larger bypass capacitor should be

connected between VIN and PGND. The bypass capacitor

should located as close to VIN and PGND as possible and

should via directly to the ground plane.

SGND (Pin 6/Pin 7): Signal Ground. Terminate the fre-

quency setting resistor and output voltage divider to SGND.

BURST (Pin 7/Pin 8): Pulse Width Modulation/Burst Mode

Selection Input. Forcing this pin low causes the switching

converter to operate in low noise ﬁxed frequency PWM

mode. Forcing this pin high enables constant Burst Mode

operation for the converter. During Burst Mode operation,

the converter can only support a reduced maximum load

current.

RT (Pin 8/Pin 9): Programs the Frequency of the Internal

Oscillator. Connect a resistor from RT to ground (SGND).

The RT resistor value for a given frequency is given by the

following equation.

T ≅

fMHz

()

VC (Pin 9/Pin 12): Error Amp Output. An R-C network is

connected from this pin to FB for loop compensation. Refer

to the Closing the Feedback Loop section for component

selection guidelines.

FB (Pin 10/Pin 13): Feedback Voltage for the Buck-Boost

Converter Derived from a Resistor Divider on the Buck-

Boost Output Voltage. The buck-boost output voltage is

given by the following equation:

OUT = 0.600 1+

⎛

⎝⎜

⎞

⎠⎟

()

where R1 is a resistor connected between FB and SGND,

and R2 is a resistor connected between FB and VOUT. The

buck-boost output voltage can be adjusted from 1.8V to

5.5V.

RUN (Pin 11/Pin 14): Active High Converter Enable In-

put. Applying a voltage <0.3V to this pin shuts down the

LTC3113. Applying a voltage >1.2V to this pin enables

the LTC3113.

SW1 (Pins 12, 13, 14/Pins 15, 16, 17): Switch Pin Where

Internal Switches A and B are Connected. Connect the

inductor from SW1 to SW2. Minimize trace length to

reduce EMI.

SW2 (Pins 15, 16/Pins 18, 19): Switch Pin Where Internal

Switches C and D are Connected. Connect the inductor

from SW1 to SW2. Minimize trace length to reduce EMI.

PGND (Exposed Pad Pin 17/Pins 1, 10, 11, 20, Exposed

Pad Pin 21): The exposed pad must be soldered to the

PCB and electrically connected to ground through the

shortest and lowest impedance connection possible.

In most applications the bulk of the heat ﬂow out of the

LTC3113 is through this pad, so printed circuit board

design has an impact on the thermal performance of the

part. See the PCB Layout and Thermal Considerations

section for more details.

(DFN/TSSOP)

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