AAT4295 데이터 시트보기 (PDF) - Skyworks Solutions

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AAT4295

Single/Dual RGB Controller

Skyworks Solutions 

Application Information

External Component Selection

The AAT4295 and AAT4297 have been designed so that

no external parts are required for the device to function

as a general purpose three- or six-position low-side

switch. For some applications, the addition of bypass

capacitors or pull-up or pull-down resistors may be

desired to improve overall system performance.

For lighting applications, such as controlling RGB LEDs,

keypad or display backlight LEDs, or photo flash LEDs,

no bypass capacitors are necessary. For other general

purpose load switching applications which may use some

or all of the outputs to switch light load current levels to

application circuits, good engineering practice would

dictate the use of small bypass capacitors placed on the

VCC input and each switch connection that is used to

conduct current from the load to ground. The use of

small ceramic capacitors between the input and output

nodes will aid in reducing line and load transient

response effects when the load switch on a given output

is turned on or off.

Input Capacitor

Typically, a 0.1μF capacitor is recommended for CIN in

most applications to provide input line transient response

immunity to small changes in the input supply. A CIN

capacitor is not required for basic operation. If used, CIN

should be located as close to the device VIN pin as prac-

tically possible.

There is no specific capacitor equivalent series resis-

tance (ESR) requirement for CIN; however, for higher

current operation, ceramic capacitors are recommended

for CIN due to their inherent capability over tantalum or

aluminum electrolytic capacitors to withstand input cur-

rent surges from low impedance sources, such as batter-

ies in portable devices.

Output Capacitor

For typical applications where the AAT4295/97 is used

for LED lighting control, no output capacitors are

required because the end load is not sensitive to device

turn-on or turn-off transient effects.

For improved load transient response in systems using

the AAT4295/97 for load switching, the addition of a

small output capacitor placed between the output pins

DATA SHEET

AAT4295/4297

Single/Dual RGB Controller

and ground can have a beneficial effect. A 0.1μF ceram-

ic capacitor is suggested as a reasonable value for an

output capacitor.

The output capacitor has no specific capacitor type or

ESR requirement. If desired, COUT may be increased to a

value greater than 0.1μF without limit to accommodate

any load transient condition without adversely affecting

the device turn-on slew rate time.

Thermal Considerations

The AAT4295 and AAT4297 are designed to sink a con-

tinuous load current to ground when a respective switch

is enabled via the S2Cwire control. The limiting charac-

teristic for maximum safe operating load current through

a given switch or set of switches is package power dis-

sipation. In order to obtain high operating currents,

careful device layout and circuit operating conditions

must be taken into account. At any given ambient tem-

perature (TA), the maximum package power dissipation

can be determined by the following equation:

PD(MAX)

=

TJ(MAX) - TA

θJA

Constants for the AAT4295 are maximum junction tem-

perature, TJ(MAX) = 125°C, and package thermal resis-

tance, JA = 225°C/W. Worst case conditions are calcu-

lated at the maximum operating temperature, where TA

= 85°C. Typical conditions are calculated under normal

ambient conditions, where TA = 25°C. At 25°C ambient,

the AAT4295 is capable of dissipating 444.4mW of power

and the AAT4297 is capable of dissipating 625mW of

power. At 85°C ambient, the AAT4295 is capable of dis-

sipating 177.8mW of power and the AAT4297 can dissi-

pate 250mW.

The power dissipation of any given MOSFET switch is

limited by its respective on resistance (RDS). The RDS of

any given MOSFET switch is controlled by the applied

gate voltage to the switch, which is set by the applied

VCC supply and the ambient operating temperature.

Switch RDS for the AAT4295 or AAT4297 may be esti-

mated by using the RDS versus Temperature curve in the

Typical Characteristics section of this datasheet. The

maximum current of any given switch can be calculated

for a given operating temperature and VCC supply level.

The corresponding RDS is determined by use of the RDS

vs. Temperature curve for the given VCC.

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com

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202309B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 11, 2013

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