MAX. ALLOWABLE CERAMIC

OUTPUT CAPACITANCE (2F)

100

1000

10

100

LOAD CURRENT (A)

STABLE REGION

0

1

2

.001

.01

0.1

1.0

10

LP3852, LP3855

www.ti.com

SNVS174I – FEBRUARY 2003 – REVISED FEBRUARY 2015

10.2.2.1.2

Output Capacitor

An output capacitor is required for loop stability. It must be located less than 1 cm from the device and connected

directly to the output and ground pins using traces which have no other currents flowing through them (see

Layout Guidelines).

The minimum amount of output capacitance that can be used for stable operation is 10 µF. For general usage

across all load currents and operating conditions, the part was characterized using a 10-µF tantalum input

capacitor. The minimum and maximum stable equivalent series resistance (ESR) range for the output capacitor

was then measured which kept the device stable, assuming any output capacitor whose value is greater than 10

µF (see Figure 20).

It should be noted that it is possible to operate the part with an output capacitor whose ESR is below these limits,

assuming that sufficient ceramic input capacitance is provided. This will allow stable operation using ceramic

output capacitors (see Operation with Ceramic Output Capacitors).

10.2.2.2 Operation with Ceramic Output Capacitors

LP385X voltage regulators can operate with ceramic output capacitors if the values of the input and output

capacitors are selected appropriately. The total ceramic output capacitance must be equal to or less than a

specified maximum value in order for the regulator to remain stable over all operating conditions. This maximum

amount of ceramic output capacitance is dependent upon the amount of ceramic input capacitance used as well

as the load current of the application. This relationship is shown in Figure 21, which graphs the maximum stable

value of ceramic output capacitance as a function of ceramic input capacitance for load currents of 1.5 A.

Figure 21. Maximum Ceramic Output Capacitance vs Ceramic Input Capacitance

If the maximum load current is 1.5 A and a 10-µF ceramic input capacitor is used, the regulator will be stable with

ceramic output capacitor values from 10 µF up to about 150 µF. When calculating the total ceramic output

capacitance present in an application, it is necessary to include any ceramic bypass capacitors connected to the

regulator output.

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