ADP1710/ADP1711
Rev. 0 | Page 10 of 16
APPLICATION INFORMATION
CAPACITOR SELECTION
Output Capacitor
The ADP1710/ADP1711 are designed for operation with small,
space-saving ceramic capacitors, but they will 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
1 μF capacitance with an ESR of 500 mΩ or less is recommended
to ensure stability of the ADP1710/ADP1711. 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 ADP1710/ADP1711 to large changes in load
current. Figure 21 and Figure 22 show the transient responses for
output capacitance values of 1 μF and 22 μF, respectively.
VIN = 5V
VOUT = 3.3V
CIN = 1µF
COUT = 1µF
TIME (4µs/DIV)
1
10mV/DI
VOUT RESPONSE TO LOAD STEP
FROM 7. 5 mA TO 14 2.5mA
06310-021
Figure 21. Output Transient Response, COUT = 1 μF
VIN = 5V
VOUT = 3.3V
CIN = 22µF
COUT = 22µF
TIME (4µs/DIV)
1
10mV/DI
VOUT RESPONSE TO LOAD STEP
FROM 7. 5 mA TO 14 2.5mA
06310-022
Figure 22. Output Transient Response, COUT = 22 μF
Input Bypass Capacitor
Connecting a 1 μF capacitor from IN 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 1 μF of output capacitance is
required, the input capacitor should be increased to match it.
Input and Output Capacitor Properties
Any good quality ceramic capacitors can be used with the
ADP1710/ADP1711, 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 temperature 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 ADP1710/ADP1711 are protected against damage due to
excessive power dissipation by current and thermal overload
protection circuits. The ADP1710/ADP1711 are designed to
current limit when the output load reaches 270 mA (typical).
When the output load exceeds 270 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, 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 ADP1710/ADP1711 current limits, so that
only 270 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
temperature cools and drops below 135°C, the output turns on
and conducts 270 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 270 mA and 0 mA, which continues as
long as the short remains at the output.