ADP1712/ADP1713/ADP1714

Rev. A | Page 12 of 16

APPLICATION INFORMATION

CAPACITOR SELECTION

Output Capacitor

The ADP1712/ADP1713/ADP1714 are designed for operation

with small, space-saving ceramic capacitors, but they function

with most commonly used capacitors as long as care is taken about

the effective series resistance (ESR) value. The ESR of the output

capacitor affects stability of the LDO control loop. A minimum of

2.2 μF capacitance with an ESR of 500 mΩ or less is recommended

to ensure stability of the ADP1712/ADP1713/ADP1714. Transient

response to changes in load current is also affected by output

capacitance. Using a larger value of output capacitance improves

the transient response of the ADP1712/ADP1713/ADP1714 to

large changes in load current. Figure 31 and Figure 32 show the

transient responses for output capacitance values of 2.2 μF and

10 μF, respectively.

TIME (20μs/DIV)

FROM 10mA TO 300mA

TIME (20μs/DIV)

FROM 10mA TO 300mA

Input Bypass Capacitor

Connecting a 2.2 μF capacitor from the IN pin to GND reduces

the circuit sensitivity to printed circuit board (PCB) layout,

especially when long input traces or high source impedance are

encountered. If greater than 2.2 μF of output capacitance is

required, increasing the input capacitor to match is recommended.

Input and Output Capacitor Properties

Any good quality ceramic capacitors can be used with the

ADP1712/ADP1713/ADP1714, as long as they meet the

minimum capacitance and maximum ESR requirements.

Ceramic capacitors are manufactured with a variety of

dielectrics, each with different behavior over temperature and

applied voltage. Capacitors must have a dielectric adequate to

ensure the minimum capacitance over the necessary temper-

ature range and dc bias conditions. X5R or X7R dielectrics with

a voltage rating of 6.3 V or 10 V are recommended. Y5V and

Z5U dielectrics are not recommended, due to their poor

temperature and dc bias characteristics.

CURRENT LIMIT AND THERMAL OVERLOAD

PROTECTION

The ADP1712/ADP1713/ADP1714 are protected against damage

due to excessive power dissipation by current and thermal over-

load protection circuits. The ADP1712/ADP1713/ADP1714 are

designed to current limit when the output load reaches 500 mA

(typical). When the output load exceeds 500 mA, the output

voltage is reduced to maintain a constant current limit.

Thermal overload protection is included, which limits the

junction temperature to a maximum of 150°C (typical). Under

extreme conditions (that is, high ambient temperature and

power dissipation), when the junction temperature starts to rise

above 150°C, the output is turned off, reducing the output

current to zero. When the junction temperature drops below

135°C (typical), the output is turned on again and output

current is restored to its nominal value.

Consider the case where a hard short from OUT to ground occurs.

At first the ADP1712/ADP1713/ADP1714 current limit, so that

only 500 mA is conducted into the short. If self heating of the

junction is great enough to cause its temperature to rise above

150°C, thermal shutdown activates, turning off the output and

reducing the output current to zero. As the junction temper-

ature cools and drops below 135°C, the output turns on and

conducts 500 mA into the short, again causing the junction

temperature to rise above 150°C. This thermal oscillation

between 135°C and 150°C causes a current oscillation between

500 mA and 0 mA, which continues as long as the short

remains at the output.

Current and thermal limit protections are intended to protect

the device against accidental overload conditions. For reliable

operation, device power dissipation needs to be externally

limited so junction temperatures do not exceed 125°C.