LTM8045 datasheet(8/22 Pages) AD

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LTM4693

Rev. 0

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OPERATION

The LTM4693 is a standalone nonisolated buck-boost

switching DC/DC power supply. The buck-boost topology

allows the LTM4693 to regulate its output voltage above

or below the input voltage, and the maximum output cur-

rent depends upon the input voltage. In buck and buck-

boost region, the converter can source 2A output current,

while in boost region, the converter can source at least

1A output current. The low RDS(ON), low gate charge syn-

chronous switches and low DCR inductor inside provide

highly efficient power module with a tiny 3.5mm × 4mm

× 1.25mm size. The LTM4693 utilizes a proprietary low

noise switching algorithm to provide a seamless transi-

tion between operating modes. These advantages result

in increased efficiency and stability in comparison to the

traditional buck-boost converter. A simplified block dia-

gram is given on the previous page.

The LTM4693 provides a precisely regulated output volt-

age programmable from 1.8V to 5.5V via an external

resistor connecting from the FB pin to GND. The input

voltage range is from 2.6V to 5.5V.

The LTM4693 utilizes average current mode control

for its pulse width modulator. Current mode control,

both average and the better known peak method, pro-

vide some benefits compared to other control methods

including: simplified loop compensation, rapid response

to load transients and inherent line voltage rejection. The

switching frequency is set by connecting the appropriate

resistor value from the FREQ pin to GND. The LTM4693

default frequency is 1MHz, and it can be configured to

operate over a wide range of switching frequencies, from

1MHz to 4MHz, allowing applications to be optimized for

broad area and efficiency. Driving the MODE/SYNC pin will

synchronize the LTM4693 to an external clock.

Burst Mode operation is available in the LTM4693 and is

user-selected via the MODE/SYNC input pin. In Burst Mode

operation, the LTM4693 provides exceptional efficiency at

light output loads by operating the converter only when

necessary to maintain voltage regulation. The typical

quiescent current in Burst Mode operation is only 15μA

at no load. At higher loads, the LTM4693 automatically

transitions to fixed frequency PWM operation. Continuous

PWM mode can also be selected via the MODE/SYNC pin

for low switching ripple and low noise operation.

The LTM4693 features an accurate, resistor programma-

ble RUN/UVLO comparator which allows the buck-boost

DC/DC converter to turn on and off at user-selected volt-

age thresholds depending on the power source. Besides,

the soft-start period is also programmable by an appropri-

ate capacitor connecting from SS to GND.

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