Datasheet

LTC3446
17
3446ff
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)
CHANGE IN VALUE (%)
3446 F03
20
0
–20
–40
–60
–80
–100
0
4
8
10
2 6
X5R
Y5V
BOTH CAPACITORS ARE 1µF,
10V, 0603 CASE SIZE
TEMPERATURE (°C)
–50
–100
CHANGE IN VALUE (%)
–80
–60
–40
–20
X5R
Y5V
20
–25
0 25 50
3446 F04
75
0
BOTH CAPACITORS ARE 1µF,
10V, 0603 CASE SIZE
1.5V VLDO OUTPUT
1.2V VLDO OUTPUT
0.5V/DIV
BOTH VLDO
ENABLES
5V/DIV
V
LVIN
= 1.8V
V
IN
= 3.6V
FRONT PAGE APPLICATION CIRCUIT
WITH 10mA RESISTOR LOADS ON
EACH VLDO OUTPUT
200µs/DIV
3446 F05