ILC7080/81

6

REV. 1.0.7 4/3/03

Maximum Output Current

The maximum output current available from the ILC7080/81

is limited by the maximum package power dissipation as

well as the device’s internal current limit. For a given ambi-

tion is given by:

and

θ

package power dissipation is;

PD(max) = 195mW.

The maximum output current can be calculated from the fol-

lowing equation:

output current, the die temperature will rise and cause the

thermal protection circuit to be enabled.

Application Hints

Figure 4 shows the typical application circuit for the

ILC7080/81.

Figure 4. Basic application circuit for fixed output voltage

Input Capacitor

ter supply noise from entering the LDO. The input capacitor

should be connected as close to the LDO regulator input pin as

is practical. Using a high-value input capacitor will offer supe-

rior line transient response as well as better power supply ripple

rejection. A ceramic or tantalum capacitor may be used at the

input of the LDO regulator.

Note that there is a parasitic diode from the LDO regulator out-

put to the input. If the input voltage swings below the regulator’s

output voltage by a couple of hundred milivolts then the regula-

tor may be damaged. This condition must be avoided. In many

powered off.

Output Capacitor Selection

Fairchild strongly recommends the use of low ESR (equivalent

ILC7080/81 is stable with low ESR capacitor (as low as zero

Ω). The value of the output capacitor should be 1µF or higher.

Either ceramic chip or a tantalum capacitor may be used at the

output.

Use of ceramic chip capacitors offer significant advantages over

tantalum capacitors. A ceramic capacitor is typically consider-

ably cheaper than a tantalum capacitor, it usually has a smaller

footprint, lower height, and lighter weight than a tantalum

capacitor. Furthermore, unlike tantalum capacitors which are

polarized and can be damaged if connected incorrectly, ceramic

capacitors are non-polarized. Low value ceramic chip capacitors

with X7R dielectric are available in the 100pF to 4.7µF range,

while high value capacitors with Y5V dielectric are available in

the 2200pF to 22µF range. Evaluate carefully before using

capacitors with Y5V dielectric because their ESR increases sig-

nificantly at cold temperatures. Figure 10 shows a list of recom-

mended ceramic capacitors for use at the output of ILC7080/81.

Note:

If a tantalum output capacitor is used then for stable

operation we recommend a low ESR tantalum capacitor with

maximum rated ESR at or below 0.4

Ω. Low ESR tantalum

capacitors, such as the TPS series from AVX Corporation

(www.avxcorp.com) or the T495 series from Kemet

(www.kemet.com) may be used.

In applications where a high output surge current can be

expected, use a high value but low ESR output capacitor for

superior load transient response. The ILC7080/81 is stable with

no load.

Noise Bypass Capacitor

In low noise applications, the self noise of the ILC7080/81 can

be decreased further by connecting a capacitor from the noise

bypass pin (pin 4) to ground (pin 2). The noise bypass pin is a

high impedance node as such, care should be taken in printed

circuit board layout to avoid noise pick-up from external

sources. Moreover, the noise bypass capacitor should have low

leakage.

Noise bypass capacitors with a value as low as 470pF may be

used. However, for optimum performance, use a 0.01µF or

larger, ceramic chip capacitor. Note that the turn on and turn off

response of the ILC7080/81 is inversely proportional to the

value of the noise bypass capacitor. For fast turn on and turn off,

use a small value noise bypass capacitor. In applications were

exceptionally low output noise is not required, consider omit-

ting the noise bypass capacitor altogether.

ILC7080

ILC7081

V

OUT

V

IN

C

OUT

SOT23-5

ON

OFF

12

3

4

5

C

NOISE