NCP698

http://onsemi.com

7

APPLICATIONS INFORMATION

A typical application circuit for the NCP698 is shown in

Figure 1.

Input Decoupling (C1)

A 1.0

mF capacitor either ceramic or tantalum is

recommended and should be connected close to the NCP698

package. Higher values and lower ESR will improve the

overall line transient response.

TDK capacitor: C2012X5R1C105K, or C1608X5R1A105K

Output Decoupling (C2)

The NCP698 is a very 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 10 W can thus safely be used.

The minimum decoupling value is 0.1

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

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.

Place 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 NCP698 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 devices have 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 NCP698 can dissipate up to

250 mW @ 25

°C.

The power dissipated by the NCP698 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 2.5

mA. For an NCP698

(3.0 V), the maximum input voltage will then be 6.0 V.

(1 oz Cu thickness)

700

500

400

200

100

150

350

190

0

600

170

250

210

230

No pin connected to Cu Plane

300

270

290

310

330

Pin 2 connected to Cu Plane