LTC3446 datasheet(18/20 Pages) LINER

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LTC3446

3446fd

APPLICATIONS INFORMATION

in more stable characteristics and are usually more suit-

able for use as the output capacitor. The X7R type has

better stability across temperature, while the X5R is less

expensive and is available in higher values. In all cases,

the output capacitance should never drop below 0.4μF, or

instability or degraded performance may occur.

VLDO Output Short-Circuit Protection

The VLDO regulators have built-in short-circuit limiting.

During short-circuit conditions, internal circuitry automati-

cally limits the output current to approximately 760mA.

VLDO Regulator Soft-Start

Each VLDO regulator includes a soft-start feature to

prevent excessive current ﬂow during start-up. When

the VLDO regulator is enabled, the soft-start circuitry

gradually increases the VLDO regulator reference voltage

from 0V to 0.4V over a period of about 600μs. There is a

short 700μs delay from the time the part is enabled until

the LDO output starts to rise. Figure 5 shows the start-up

output waveform.

Figure 3. Ceramic Capacitor DC Bias Characteristics

Figure 4. Ceramic Capacitor Temperature Characteristics

Figure 5. VLDO Regulator Output Start-Up

DC BIAS VOLTAGE (V)

3446 F03

–20

–40

–60

–80

–100

X5R

Y5V

BOTH CAPACITORS ARE 1μF,

10V, 0603 CASE SIZE

TEMPERATURE (°C)

–50

–100

–80

–60

–40

–20

X5R

Y5V

–25

025

3446 F04

BOTH CAPACITORS ARE 1μF,

10V, 0603 CASE SIZE

1.5V VLDO OUTPUT

1.2V VLDO OUTPUT

0.5V/DIV

BOTH VLDO

ENABLES

5V/DIV

VLVIN = 1.8V

VIN = 3.6V

FRONT PAGE APPLICATION CIRCUIT

WITH 10mA RESISTOR LOADS ON

EACH VLDO OUTPUT

200μs/DIV

3446 F05

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