ADP160/ADP161

Rev. 0 | Page 13 of 20

APPLICATIONS INFORMATION

CAPACITOR SELECTION

Output Capacitor

The ADP160/ADP161 are designed for operation with small,

space-saving ceramic capacitors, but functions with most

commonly used capacitors as long as care is with regard to 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 1 Ω or less is recommended

to ensure stability of the ADP160/ADP161. 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 ADP160/ADP161 to large changes in load current.

Figure 30 and Figure 31 show the transient responses for output

capacitance values of 1 μF and 10 μF, respectively.

CH1 100mA

Ω CH2 200mV

M200µs

A CH1

62mA

1

2

T

LOAD CURRENT

CH1 100mA

Ω CH2 200mV

M200µs

A CH1

74mA

1

2

T

LOAD CURRENT

Input Bypass Capacitor

Connecting a 1 μF capacitor from VIN to GND reduces the circuit

sensitivity to the 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 ADP160/

ADP161, 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.

Figure 32 depicts the capacitance vs. voltage bias characteristic

of a 0402, 1 μF, 10 V, X5R capacitor. The voltage stability of a

capacitor is strongly influenced by the capacitor size and voltage

rating. In general, a capacitor in a larger package or higher voltage

rating exhibits better stability. The temperature variation of the X5R

dielectric is about ±15% over the −40°C to +85°C temperature

range and is not a function of package or voltage rating.

1.2

1.0

0.8

0.6

0.4

0.2

0

024

68

1

VOLTAGE

0

Figure 32. Capacitance vs. Voltage Characteristic

Use Equation 1 to determine the worst-case capacitance accounting

for capacitor variation over temperature, component tolerance,

and voltage.

(1)

where:

TEMPCO is the worst-case capacitor temperature coefficient.

TOL is the worst-case component tolerance.

In this example, the worst-case temperature coefficient (TEMPCO)

over −40°C to +85°C is assumed to be 15% for an X5R dielectric.

The tolerance of the capacitor (TOL) is assumed to be 10%, and

Substituting these values in Equation 1 yields

Therefore, the capacitor chosen in this example meets

the minimum capacitance requirement of the LDO over

temperature and tolerance at the chosen output voltage.