ST2L01 データシートの表示（PDF） - STMicroelectronics

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ST2L01

DUAL VOLTAGE REGULATOR

STMicroelectronics 

ST2L01

APPLICATION HINTS

EXTERNAL CAPACITORS

Like any low-dropout regulator, the ST2L01

requires external capacitors for stability. We

suggest to solder both capacitors as close as

possible to the relative pins (1, 2 and 5).

INPUT CAPACITORS

An input capacitor, whose value is at least 1µF, is

required; the amount of the input capacitance can

be increased without limit if a good quality

tantalum or aluminum capacitor is used.

SMS X7R or Y5V ceramic multilayer capacitors

could not ensure stability in any condition because

of their variable characteristics with Frequency

and Temperature; the use of this capacitor is

strictly related to the use of the output capacitors.

For more details read the "OUTPUT CAPACITOR

SECTION".

The input capacitor must be located at a distance

of not more than 0.5" from the input pin of the

device and returened to a clean analog ground.

OUTPUT CAPACITOR

The ST2L01 is designed specifically to work with

Ceramic and Tantalum capacitros.

Special care must be taken when a Ceramic

multilayer capacitor is used.

Special care must be taken when a Ceramic

multilayer capacitor is used.

Due to their characteristics they can sometimes

have an ESR value lower than the minimum

required by the ST2L01 and their relatively large

capacitance can change a lot with the ambient

temperature.

The test results of the ST2L01 stability using

multilayer ceramic capacitors show that a

minimum value of 1µF is needed for the adjustable

regulator (set to 2.5V). This value can be

increased up to 10µF when a tantalum capacitor

is used on the input. A higher value CO can have

an ESR lower than the accepted minimum.

When a ceramic capacitor is used on the input the

output capacitance must be in the range from 1µF

to 2.2µF if CI=1µF, and from 1µF to 4.7µF if

CI=2.2µF.

The 3.3V regulator stable with a 470nF capacitor.

This value can be increased up to 10µF if a

tantalum capacitor is used on the input. A higher

value CO can have an ESR lower than the

accepted minimum.

When a ceramic capacitor is used in the input the

output capacitance must be in the range from 1µF

to 2.2µF if CI=1µF, and from 1µF to 4.7µF if

CI=2.2µF.

Surface-mountable solid tantalum capacitors offer

a good combination of small physical size for the

capacitance value and ESR in the range needed

by the ST2L01. The test results show good

stability for both outputs with values of at least

1µF. The value can be increased without limit for

even better performance such a transient

response and noise.

IMPORTANT; The output capacitor must maintain

its ESR in the stable region over the full operating

temperature to assure stability. Also , capacitor

tolerance and variation with temperature must be

considered to assure that the minimum amount of

capacitance is provided at all times. For this

reason, when a ceramic multilayer capacitor is

used, the better choise for temperature coefficent

is the X7R type, which holds the capacitance

within ±15% . The output capacitor should be

located not more than 0.5" from the output pins of

the device and returned to a clean analog ground.

ADJUSTABLE REGULATOR

The ST2L01 has a 1.25V reference voltage

between the output and the adjustable pins

(respectevely pin 4 and 2). When a resistor R2 is

placed between these two therminals a constant

current flows through R2 and down to R1 to set

the overall (VO2 to GND) output voltage.

Minimum load current is 1mA.

IADJ is very small (typically 35µA) and constant; in

the VO calculation it can be ignored.

5/12

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