NCP502, NCP502A

http://onsemi.com

7

APPLICATIONS INFORMATION

A typical application circuit for the NCP502/A series is

shown in Figure 1, front page.

Input Decoupling (C1)

A 1.0

mF capacitor either ceramic or tantalum is

recommended and should be connected close to the

NCP502/A package. Higher values and lower ESR will

improve the overall line transient response. If large line or

load transients are not expected, then it is possible to operate

the regulator without the use of a capacitor.

TDK capacitor: C2012X5R1C105K, or C1608X5R1A105K

Output Decoupling (C2)

The NCP502/A is a stable regulator and does not require

any specific Equivalent Series Resistance (ESR) or a

minimum output current. Capacitors exhibiting ESRs

ranging from a few m

W up to 5.0 W can thus safely be used.

The minimum decoupling value is 1.0

mF and can be

augmented to fulfill stringent load transient requirements.

The regulator accepts ceramic chip capacitors as well as

tantalum devices. Larger values improve noise rejection and

load regulation transient response.

TDK capacitor: C2012X5R1C105K, C1608X5R1A105K,

or C3216X7R1C105K

Enable Operation

The enable pin will turn on the regulator when pulled high

and turn off the regulator when pulled low. These limits of

threshold are covered in the electrical specification section

of this data sheet. If the enable is not used then the pin should

Hints

Please be sure the Vin and GND lines are sufficiently

wide. When the impedance of these lines is high, there is a

chance to pick up noise or cause the regulator to

malfunction.

Set external components, especially the output capacitor,

as close as possible to the circuit, and make leads as short as

possible.

Thermal

As power across the NCP502/A 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

configuration on the PCB, the board material and also the

ambient temperature effect the rate of temperature rise for

the part. This is stating that when the NCP502/A has good

thermal conductivity through the PCB, the junction

temperature will be relatively low with high power

dissipation applications.

The maximum dissipation the package can handle is

given by:

PD +

TJ(max) *TA

RqJA

If junction temperature is not allowed above the

maximum 125

°C, then the NCP502/A can dissipate up to

250 mW @ 25

°C.

The power dissipated by the NCP502/A can be calculated

from the following equation:

Ptot + [Vin *Ignd (Iout)] ) [Vin * Vout] *Iout

or

VinMAX +

Ptot ) Vout * Iout

Ignd ) Iout

If an 80 mA output current is needed then the ground

current from the data sheet is 40

mA. For an NCP502/A

(3.0 V), the maximum input voltage will then be 6.12 V.