LTC3113 datasheet(11/32 Pages) AD

11 / 32 page

LT3154

Rev. 0

For more information www.analog.com

QUICK REFERENCE

Thissectionofthedatasheetcontainsequationsforexternal

component selection for the LT3154 where applicable.

VIN UVLO Threshold

The VIN threshold is internally set to a typical value of

1.7V for turn‑on and 1.6V for turn‑off when EN/UVLO

is connected to VIN. The VIN UVLO can be adjusted to a

higher threshold voltage with a resistor network on EN/

UVLO according to the following equations:

V(TURNON) =1.2V 1+

⎛

⎝

⎜

⎞

⎠

⎟

V(TURNOFF) =1.1V 1+

⎛

⎝⎜

⎞

⎠⎟

EN/UVLO

LT3154

VIN

3154 QR01

Output Voltage Programming

The output voltage for the LT3154 is set via a resistor

divider connected at the FB pin:

VOUT = 0.99V 1+

⎛

⎝⎜

⎞

⎠⎟

LT3154

VOUT

3154 QR02

Inmostapplications,choosingR4equalto1Megrepresents

agoodtrade‑offbetweenquiescentcurrentandrobustness

against PCB leakage. The minimum recommended VOUT

setting is 1.8V, the maximum is 5.5V.

Switching Frequency

The buck‑boost converter switching frequency, fSW, is

set by the value of the RT resistor connected between the

RT pin and ground according to the following equation.

Connecting the RT pin to VIN will set a default frequency

of 2.2MHz.

fSW(MHz)=

110

(kΩ)

PROGRAMMABLE

FREQUENCY

DEFAULT 2.2MHz

FREQUENCY

VIN

3154 QR04

Table 1. RT Value for Common Switching Frequencies

fSW

400kHz

274kΩ

500kHz

221kΩ

750kHz

147kΩ

1.0MHz

110kΩ

2.0MHz

54.9kΩ

2.2MHz

Connect to VIN

3.0MHz

36.5kΩ

4.0MHz

27.4kΩ

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