NCP148

www.onsemi.com

10

APPLICATIONS INFORMATION

General

The NCP148 is an ultra−low noise 450 mA low dropout

regulator designed to meet the requirements of RF

applications and high performance analog circuits. The

NCP148 device provides very high PSRR and excellent

dynamic response. In connection with low quiescent current

this device is well suitable for battery powered application

such as cell phones, tablets and other. The NCP148 is fully

protected in case of current overload, output short circuit and

overheating.

Input capacitor connected as close as possible is necessary

for ensure device stability. The X7R or X5R capacitor

should be used for reliable performance over temperature

range. The value of the input capacitor should be 1

mF or

greater to ensure the best dynamic performance. This

capacitor will provide a low impedance path for unwanted

AC signals or noise modulated onto constant input voltage.

There is no requirement for the ESR of the input capacitor

but it is recommended to use ceramic capacitors for their low

ESR and ESL. A good input capacitor will limit the

influence of input trace inductance and source resistance

during sudden load current changes.

The NCP148 requires an output capacitor connected as

close as possible to the output pin of the regulator. The

recommended capacitor value is 1

mF and X7R or X5R

dielectric due to its low capacitance variations over the

specified temperature range. The NCP148 is designed to

remain stable with minimum effective capacitance of 0.7

mF

to account for changes with temperature, DC bias and

package size. Especially for small package size capacitors

such as 0201 the effective capacitance drops rapidly with the

applied DC bias. Please refer Figure 37.

Figure 37. Capacity vs DC Bias Voltage

There is no requirement for the minimum value of

maximum value of ESR should be less than 2

Ω. Larger

output capacitors and lower ESR could improve the load

transient response or high frequency PSRR. It is not

recommended to use tantalum capacitors on the output due

to their large ESR. The equivalent series resistance of

tantalum capacitors is also strongly dependent on the

temperature, increasing at low temperature.

Enable Operation

The NCP148 uses the EN pin to enable/disable its device

and to deactivate/activate the active discharge function.

If the EN pin voltage is <0.4 V the device is guaranteed to

be disabled. The pass transistor is turned−off so that there is

virtually no current flow between the IN and OUT. The

active discharge transistor is active so that the output voltage

Ω resistor. In the

disable state the device consumes as low as typ. 10 nA from

If the EN pin voltage >1.2 V the device is guaranteed to

be enabled. The NCP148 regulates the output voltage and

the active discharge transistor is turned−off.

The EN pin has internal pull−down current source with

typ. value of 200 nA which assures that the device is

turned−off when the EN pin is not connected. In the case

where the EN function isn’t required the EN should be tied

directly to IN. After device is enabled by EN pin soft start

feature ensure that maximal Vout slew rate will be slower

than 30 mV/

ms. The soft start function also protects powered

device before possible damage by large inrush current.

Output Current Limit

Output Current is internally limited within the IC to a

typical 700 mA. The NCP148 will source this amount of

current measured with a voltage drops on the 90% of the

the output current to 690 mA (typ). The current limit and

short circuit protection will work properly over whole

temperature range and also input voltage range. There is no

limitation for the short circuit duration.

Thermal Shutdown

When the die temperature exceeds the Thermal Shutdown

* 160°C typical), Thermal Shutdown event

is detected and the device is disabled. The IC will remain in

this state until the die temperature decreases below the

°C typical).

Once the IC temperature falls below the 140

°C the LDO is

enabled again. The thermal shutdown feature provides the

protection from a catastrophic device failure due to

accidental overheating. This protection is not intended to be

used as a substitute for proper heat sinking.

Power Dissipation

As power dissipated in the NCP148 increases, it might

become necessary to provide some thermal relief. The

maximum power dissipation supported by the device is

dependent upon board design and layout. Mounting pad