Datasheet ADP1710, ADP1711 (Analog Devices) - 10

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ADP1710/ADP1711 APPLICATION INFORMATION CAPACITOR SELECTION Input Bypass Capacitor Output Capacitor
Connecting a 1 μF capacitor from IN to GND reduces the The ADP1710/ADP1711 are designed for operation with small, circuit sensitivity to printed circuit board (PCB) layout, space-saving ceramic capacitors, but they will function with most especially when long input traces or high source impedance are commonly used capacitors as long as care is taken about the encountered. If greater than 1 μF of output capacitance is effective series resistance (ESR) value. The ESR of the output required, the input capacitor should be increased to match it. capacitor affects stability of the LDO control loop. A minimum of
Input and Output Capacitor Properties
1 μF capacitance with an ESR of 500 mΩ or less is recommended to ensure stability of the ADP1710/ADP1711. Transient response Any good quality ceramic capacitors can be used with the to changes in load current is also affected by output capacitance. ADP1710/ADP1711, as long as they meet the minimum Using a larger value of output capacitance improves the transient capacitance and maximum ESR requirements. Ceramic response of the ADP1710/ADP1711 to large changes in load capacitors are manufactured with a variety of dielectrics, each current. Figure 21 and Figure 22 show the transient responses for with different behavior over temperature and applied voltage. output capacitance values of 1 μF and 22 μF, respectively. 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
VOUT RESPONSE TO LOAD STEP FROM 7.5mA TO 142.5mA
and dc bias characteristics.
IV CURRENT LIMIT AND THERMAL OVERLOAD /D V 1 PROTECTION 10m
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
VIN = 5V VOUT = 3.3V
current limit when the output load reaches 270 mA (typical).
CIN = 1µF C
When the output load exceeds 270 mA, the output voltage is
OUT = 1µF
1 02 0- reduced to maintain a constant current limit.
TIME (4µs/DIV)
31 06 Figure 21. Output Transient Response, COUT = 1 μF 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
V
above 150°C, the output is turned off, reducing the output
OUT RESPONSE TO LOAD STEP FROM 7.5mA TO 142.5mA
current to zero. When the junction temperature drops below
V
135°C, the output is turned on again and output current is
/DI V 1
restored to its nominal value.
10m
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
VIN = 5V
junction is great enough to cause its temperature to rise above
VOUT = 3.3V CIN = 22µF
150°C, thermal shutdown activates, turning off the output and
COUT = 22µF
2 02 0- reducing the output current to zero. As the junction
TIME (4µs/DIV)
31 06 temperature cools and drops below 135°C, the output turns on Figure 22. Output Transient Response, COUT = 22 μF 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. Rev. 0 | Page 10 of 16 Document Outline FEATURES APPLICATIONS TYPICAL APPLICATION CIRCUITS GENERAL DESCRIPTION TABLE OF CONTENTS REVISION HISTORY SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS THERMAL RESISTANCE ESD CAUTION PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS THEORY OF OPERATION ADJUSTABLE OUTPUT VOLTAGE (ADP1710 ADJUSTABLE) BYPASS CAPACITOR (ADP1711) ENABLE FEATURE UNDERVOLTAGE LOCKOUT (UVLO) APPLICATION INFORMATION CAPACITOR SELECTION CURRENT LIMIT AND THERMAL OVERLOAD PROTECTION THERMAL CONSIDERATIONS PRINTED CIRCUIT BOARD LAYOUT CONSIDERATIONS OUTLINE DIMENSIONS ORDERING GUIDE