LTC3113 datasheet(9/32 Pages) AD

9 / 32 page

LT3154

Rev. 0

For more information www.analog.com

PIN FUNCTIONS

PVIN (Pins 1, 2): Power Input for Buck‑Boost Converter.

Connect a minimum 22μF low ESR capacitor to PGND

as close to the device as possible. This pin must be con‑

nected to VIN in application.

VIN (Pin 3): Signal Input Voltage. Decouple with minimum

1µF capacitor. Low noise input for control circuitry.

EN/UVLO (Pin 4): Input to Enable the IC. Connect EN/

UVLO to VIN to enable the LT3154 at the 1.8V minimum

operating voltage. Connect to an external divider from

VIN to provide a programmable accurate VIN undervolt‑

age threshold:

V(TURNON) =1.2V 1+

⎛

⎝

⎜

⎞

⎠

⎟

The accurate EN/UVLO pin threshold has 100mV of hys‑

teresis provided internally:

V(TURNOFF) =1.1V 1+

⎛

⎝

⎜

⎞

⎠

⎟

An external capacitor is recommended if EN/UVLO

is digitally controlled (see Note 7 in the Electrical

Characteristics section).

SYNC/MODE (Pin 5): Burst Mode operation Select and

Oscillator Synchronization. Do not leave this pin floating.

SYNC/MODE = High (VIN). Disable Burst Mode

Operation and maintain low noise, constant frequency

PWM operation.

SYNC/MODE = Low (GND). The converter operates in

Automatic Burst Mode operation.

SYNC/MODE = External CLK. The internal oscillator is syn‑

chronized to the external CLK signal, Burst Mode opera‑

tion is disabled. A clock pulse width between 75ns and

T period –75ns is required to synchronize the oscillator.

An external resistor must be connected between RT and

GND to program the oscillator 25% to 50% below the

desired synchronization frequency.

RT (Pin 6): Oscillator Frequency Programming Input.

Connect to VIN for 2.2MHz fixed frequency operation.

Connect an external resistor from RT to GND to program

the switching frequency according to the formula:

RT (kΩ)=

110

fSW (MHz)

GND (Pin 7): Signal Ground. Low noise ground for

control circuits.

SS (Pin 8): External Soft Start. Connect to VIN for 2.2ms

default soft‑start period. Connect an external capacitor to

set soft start period according to the formula:

tSS (ms) = 0.8 × CSS (nF)

FB (Pin 9): Feedback Input to Error Amplifier. The resistor

divider connected to this pin sets the converter output voltage.

VOUT = 0.99V 1+

⎛

⎝⎜

⎞

⎠⎟

VC (Pin 10): Voltage error amplifier VC is used to program

average inductor current. An R‑C from this pin to ground

sets the voltage loop compensation.

VOUT (Pin 11): Signal Output Voltage. Decouple with

minimum 1µF capacitor. Low noise input for VOUT con‑

trol circuitry.

PVOUT (Pin 12): Power Output for Buck‑Boost Converter.

Connect a minimum 68μF (see Table 3 low ESR capacitor to

PGND as close to the device as possible. Capacitor value may

change depending on VOUT voltage and load current require‑

ments. This pin must be connected to VOUT in application.

SW2 (Pin 13): Buck‑Boost Converter Switch Pin. Connect

inductor between SW1 and SW2 pins.

PGND (Pins 14, 15, 17-Exposed Pad): Power Ground

Connection. These pins and exposed thermal pad must

make full connection to PCB ground plane to meet speci‑

fied thermal requirements. PGND must be connected to

the GND pin in the application.

SW1 (Pin 16): Buck‑Boost Converter Switch Pin. Connect

inductor between SW1 and SW2 pins.

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