EUP7201

DS7201 Ver 1.5 Oct. 2007

10

Application Note

External Capacitors

Like any low-dropout regulator, the EUP7201 requires

external capacitors for regulator stability. The EUP7201 is

specifically designed for portable applications requiring

minimum board space and smallest components. These

capacitors

must

be

correctly

selected

for

good

performance.

Input Capacitor

An input capacitance of

EUP7201 input pin and ground (the amount of the

capacitance may be increased without limit).

This capacitor must be located a distance of not more than

1cm from the input pin and returned to a clean analog

ground. Any good quality ceramic, tantalum, or film

capacitor may be used at the input.

If a tantalum capacitor is used at the input, it must be

guaranteed by the manufacturer to have a surge current

rating sufficient for the application.

There are no requirements for the ESR on the input

capacitor, but tolerance and temperature coefficient must

be considered when selecting the capacitor to ensure the

capacitance will be

temperature range.

Output Capacitor

The EUP7201 is designed specifically to work with very

small ceramic output capacitors. A ceramic capacitor

(temperature characteristics X7R, X5R, Z5U, or Y5V) in 1

to 22µF range with 5mΩ to 500mΩ ESR range is suitable

in the EUP7201 application circuit.

The output capacitor must meet the requirement for

minimum amount of capacitance and also have an ESR

(Equivalent Series Resistance) value which is within a

stable range (5mΩ to 500mΩ)

No-Load Stability

The EUP7201 will remain stable and in regulation with no

external load. This is specially important in CMOS RAM

keep-alive applications.

Capacitor Characteristics

The EUP7201 is designed to work with ceramic

capacitors on the output to take advantage of the benefits

they offer: for capacitance values in the range of 1µF to

4.7µF range, ceramic capacitors are the smallest, least

expensive and have the lowest ESR values (which makes

them best for eliminating high frequency noise). The

ESR of a typical 1µF ceramic capacitor is in the range of

20mΩ to 40mΩ, which easily meets the ESR requirement

for stability by the EUP7201.

The ceramic capacitor’s capacitance can vary with

temperature. The capacitor type X7R, which operates

over a temperature range of -55°C to +125°C, will only

vary the capacitance to within ±15%. Most large value

ceramic capacitors (

or Y5V temperature characteristics. Their capacitance

can drop by more than 50% as the temperature goes from

25°C to 85°C. Therefore, X7R is recommended over Z5U

and Y5V in applications where the ambient temperature

will change significantly above or below 25°C.

On/Off Input Operation

and turned on by pulling it high. If this feature is not used,

output on at all time. To assure proper operation, the

to swing above and below the specified turn-on/off

voltage thresholds listed in the Electrical Characteristics