AAT3134ISN-T1(2004) データシートの表示（PDF） - Analog Technology Inc

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AAT3134ISN-T1
(Rev.:2004)

High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications

Analog Technology Inc 

AAT3134

High Efficiency 1X/1.5X Fractional

Charge Pump for White LED Applications

Capacitor Characteristics

Ceramic composition capacitors are highly recom-

mended over all other types of capacitors for use

with the AAT3134. Ceramic capacitors offer many

advantages over their tantalum and aluminum elec-

trolytic counterparts. A ceramic capacitor typically

has very low ESR, is lowest cost, has a smaller

PCB footprint and is non-polarized. Low ESR

ceramic capacitors help maximize charge pump

transient response. Since ceramic capacitors are

non-polarized, they are not prone to incorrect con-

nection damage.

Equivalent Series Resistance (ESR)

ESR is an important characteristic to consider when

selecting a capacitor. ESR is a resistance internal

to a capacitor, which is caused by the leads, inter-

nal connections, size or area, material composition

and ambient temperature. Capacitor ESR is typi-

cally measured in milliohms for ceramic capacitors

and can range to more than several ohms for tanta-

lum or aluminum electrolytic capacitors.

Additional Application Circuits

Ceramic Capacitor Materials

Ceramic capacitors less than 0.1µF are typically

made from NPO or COG materials. NPO and COG

materials typically have tight tolerance and are stable

over temperature. Large capacitor values are typi-

cally composed of X7R, X5R, Z5U or Y5V dielectric

materials. Large ceramic capacitors, typically greater

than 2.2µF are often available in low cost Y5V and

Z5U dielectrics, but capacitors greater than 1µF are

typically not required for AAT3134 applications.

Capacitor area is another contributor to ESR.

Capacitors that are physically large will have a lower

ESR when compared to an equivalent material

smaller capacitor. These larger devices can improve

circuit transient response when compared to an

equal value capacitor in a smaller package size

Thermal Protection

The AAT3134 has a thermal protection circuit that

will shut down the internal LDO and charge pump if

the die temperature rises above the thermal limit as

is the case during a short circuit of the OUT pin.

VBATTERY

VIN

C1+

C1

1µF

VOUT

C1-

C2+

CIN

1µF

COUT

1µF

AAT3134

C2

1µF

C2-

EN/SET

D1

D2

D3

D4

EN/SET

D5

D6

GND

D1

D2

D3

D4

RB*

RB*

RB*

RB*

Resistor R is optional

D5

D6

R

R

Resistor R is optional

*In some applications, white LED forward voltages (VF) can vary significantly. Ballast resistors between the LED cathodes and ground are recommended

for balancing the forward voltage differences. The ballast resistor value may be approximated by the following equation:

RB

=

VSOURCE

IF

-

VF

3134.2004.04.1.0

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