MC33263(2006) データシートの表示（PDF） - ON Semiconductor

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MC33263
(Rev.:2006)

Ultra Low Noise 150 mA Low Dropout Voltage Regulator with ON/OFF Control

ON Semiconductor 

MC33263

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 MC33263 package. Higher values will correspondingly

improve the overall line transient response.

Output Decoupling − Due to a novel concept, the

MC33263 is a stable component and does not require any

Equivalent Series Resistance (ESR) neither a minimum

output current. Capacitors exhibiting ESRs ranging from a

few mW 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 Performances − Unlike other LDOs, the MC33263

is a true low−noise regulator. With a 10 nF bypass capacitor,

it typically reaches the incredible level of 25 mVRMS overall

noise between 100 Hz and 100 kHz. To give maximum

insight on noise specifications, ON Semiconductor includes

spectral density graphics as well as noise dependency versus

bypass capacitor.

The bypass capacitor impacts the start−up phase of the

MC33263 as depicted by the data−sheet curves. A typical

1.0 ms settling time is achieved with a 10 nF bypass

capacitor. However, due to its low−noise architecture, the

MC33263 can operate without bypass and thus offers a

typical 20 ms start−up phase. In that case, the typical output

noise stays lower than 65 mVRMS between 100 Hz −

100 kHz.

Protections − The MC33263 hosts several protections,

conferring natural ruggedness and reliability to the products

implementing the component. The output current is

internally limited to a minimum of 175 mA while

temperature shutdown occurs if the die heats up beyond

150°C. These value lets 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

+

TJmax –

RqJA

TA

If TJmax is internally limited to 150°C, then the MC33263

can dissipate up to 595 mW @ 25°C.

The power dissipated by the MC33263 can be calculated

from the following formula:

Ptot + ǀVin @ Ignd(Iout)ǁ ) ǀVin * Vout ǁ @ Iout

or

Vinmax

+

Ptot ) Vout @ Iout

Ignd ) Iout

If a 150 mA output current is needed, the ground current

is extracted from the data−sheet curves: 6.5 mA @ 150 mA.

For a MC33263NW28R2 (2.8 V), the maximum input

voltage will then be 6.48 V, a rather comfortable margin.

Typical Application − The following figure portraits the

typical application for the MC33263 where both

input/output decoupling capacitors appear.

Input

Output

654

C3

1.0 mF

MC33263

123

On/Off

C1

10 nF

C2

1.0 mF

Figure 2. A Typical MC33263 Application with

Recommended Capacitor Values (QFN6)

As for any low noise designs, particular care has to be

taken when tackling Printed Circuit Board (PCB) layout.

The following figure gives an example of a layout where

stray inductances/capacitances are minimized.

Figure 3. Printed Circuit Board

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