NCP4688

http://onsemi.com

11

APPLICATION INFORMATION

A typical application circuit for NCP4688 series is shown

in the Figure 41.

VIN

VOUT

CE

GND

C1

C2

VIN

VOUT

NCP4688x

Figure 41. Typical Application Schematic

1.0 mF

1.0 mF

Input Decoupling Capacitor (C1)

A 1.0

mF ceramic input decoupling capacitor should be

connected as close as possible to the input and ground pin of

the NCP4688 device. Higher values and lower ESR

improves line transient response.

Output Decoupling Capacitor (C2)

A 1.0

mF ceramic output decoupling capacitor is sufficient

to achieve stable operation of the device. If tantalum

capacitor is used, and its ESR is high, the loop oscillation

may result. For information about ESR see Figures 42, 43

and 44. The capacitor should be connected as close as

possible to the output and ground pin. Larger values and

lower ESR improves dynamic parameters.

Enable Operation

The enable pin CE may be used for turning the regulator

on and off. The IC is switched on when a high level voltage

is applied to the CE pin. The enable pin has an internal pull

down current source which assure off state of LDO in case

the CE pin will stay floating. If the enable function is not

The D version of the NCP4688 device includes a

discharging of the output capacitor. This function is

activated when the IC goes into disable mode.

Thermal Consideration

As a power across the IC increase, 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 configuration

on the PCB, the board material, and also the ambient

temperature affect the rate of temperature increase for the

part. When the device has good thermal conductivity

through the PCB the junction temperature will be relatively

low in high power dissipation applications.

ESR vs. Output Current

When using the NCP4688 devices, consider the following

points:

The relation between Output Current Iout and ESR of the

output capacitor are shown below in Figures 42, 43 and 44.

The conditions when the device performs stable operation

are marked as the hatched area in the charts.

Figure 42. ESR vs. Load Current NCP4688xx12

Figure 43. ESR vs. Load Current NCP4688xx25

LOAD CURRENT (mA)

LOAD CURRENT (mA)

150

125

100

75

50

25

0

0.01

0.1

1

10

100

150

125

100

75

50

25

0

0.01

0.1

1

10

100