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LTC3100

3100fa

APPLICATIONS INFORMATION

LDO Output Capacitor Selection

The LDO is designed to be stable with a minimum 1μF

output capacitor. No series resistor is required when using

low ESR capacitors. For most applications, a 2.2μF ceramic

capacitor is recommended. Larger values will improve

transient response, and raise the power supply rejection

ratio (PSRR) of the LDO. Refer to the Typical Performance

Characteristics for the allowable range of output capacitor

to ensure loop stability.

LDO Output Voltage Programming

The output voltage is set by a resistive divider according

to the following formula:

OUT =+

⎛

⎝⎜

⎞

⎠⎟

0 600

.•

The external divider is connected to the output as shown

in the Block Diagram. For improved transient response,

a feedforward capacitor may be placed in parallel with

resistor R4.

TYPICAL APPLICATIONS

Single-Cell Boost and Buck with Voltage Sequencing

Output Voltages During Soft-Start

for Sequenced Converter

SWBST

VINBK VBST

LTC3100

FBBST

3.3μH

3.5V

523k

10μF

CIN

2.2μF

VLDO

VINBST

FBLDO

SWBK

PGBK

PGBST

115k

25.5k

VBATT

0.9V TO 1.5V

2.2μF

FBBK

10μF

MODE

RUNBST

RUNLDO

RUNBK

GND

FF EN_BURST

OFF ON

3.3μH

+3.3V AT 50mA

V_I/O

120mA AT VBATT = 0.9V

220mA AT VBATT = 1.2V

V_CORE = 1.2V

BOOST_GOOD

BUCK_GOOD

3100 TA02b

1ms/DIV

VCORE, 1V/DIV

VBST, 1V/DIV

VI/O, 1V/DIV

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