MC33761

http://onsemi.com

6

APPLICATION HINTS

Input Decoupling

As with any regulator, it is necessary to reduce the

dynamic impedance of the supply rail that feeds the

component. A 1.0

mF capacitor either ceramic or tantalum is

recommended and should be connected close to the

MC33761 package. Higher values will correspondingly

improve the overall line transient response.

Output Decoupling

Thanks to a novel concept, the MC33761 is a stable

component and does not require any specific Equivalent

Series Resistance (ESR) neither a minimum output current.

Capacitors exhibiting ESRs ranging from a few m

W up to

3.0

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.

Noise Decoupling

Unlike other LDOs, the MC33761 is a true low−noise

regulator. Without the need of an external bypass capacitor,

it typically reaches the incredible level of 40

mVRMS overall

noise between 100 Hz and 100 kHz. To give maximum

insight on noise specifications, ON Semiconductor includes

spectral density graphics. The classical bypass capacitor

impacts the start−up phase of standard LDOs. However,

thanks to its low−noise architecture, the MC33761 operates

without a bypass element and thus offers a typical 40

ms

start−up phase.

Protections

The MC33761 hosts several protections, giving natural

ruggedness and reliability to the products implementing the

component. The output current is internally limited to a

maximum value of 180 mA typical while temperature

shutdown occurs if the die heats up beyond 125

°C. These

values let you assess the maximum differential voltage the

device can sustain at a given output current before its

protections come into play.

The maximum dissipation the package can handle is given

by:

Pmax +

T

Jmax *

T

A

RqJA

dissipate up to 470 mW @ 25

°C. The power dissipated by

the MC33761 can be calculated from the following formula:

Ptot

+ V

in

I

gnd

(Iout) ) Vin * Vout

Iout

or

Vinmax +

Ptot

) V

out

Iout

I

gnd )

Iout

If a 80 mA output current is needed, the ground current is

extracted from the data−sheet curves: 4.0 mA @ 80 mA. For

a MC33761SNT1−28 (2.8 V) delivering 80 mA and

operating at 25

°C, the maximum input voltage will then be

8.3 V.

Typical Applications

The following picture portrays the typical application of

the MC33761.