PAM3110AMB150R datasheet(7/13 Pages) PAM

7 / 13 page

PAM3110

www.poweranalog.com

Power Analog Microelectronics Inc

The PAM3110 fa mily of low-drop ou t (L DO)

regulators have several features that allow them

to apply to a wide range of applications. The

family operates with very low input voltage and

low dropout voltage (typically 300mV at full load),

making it an efficient stand-alone power supply or

post regulator for battery or switch mode power

supplies. The 1.5A output current make the

PAM3110 family suitable for powering many

microprocessors and FPGA supplies.

A 4.7µF or larger ceramic input bypass capacitor,

connected between V

and GND and located

close to the PAM3110, is required for stability. A

4.7 F minimum value capacitor from V to GND is

also required. To improve transient response,

noise rejection, and ripple rejection, an additional

1 0 µF

o r

l a r g e r ,

l o w

E S R

c a p a c i t o r

i s

recommended at the output. A higher-value, low

ESR output capacitor may be necessary if large,

fast-rise-time load transients are anticipated and

the device is located several inches from the

power source, especially if the minimum input

voltage of 2.5 V is used.

The PAM3110 features internal current limiting,

thermal protection and short circuit protection.

During normal operation, the PAM3110 limits

output current to about 2A. When current limiting

engages, the output voltage scales back linearly

until the over current condition ends. While

current limiting is designed to prevent gross

device failure, care should be taken not to exceed

the power dissipation ratings of the package. If

the temperature of the device exceeds 150°C,

thermal-protection circuitry will shut down. Once

the device has cooled down to approximately

30°C below the high temp trip point, regulator

operation resumes. The short circuit current of

the PAM3110 is about 0.5A when its output pin is

shorted to ground.

The amount of heat that an LDO linear regulator

generates is:

P =(V -V )I .

All integrated circuits have a maximum allowable

junction temperature (T

max) above which

normal operation is not assured. A system

designer must design the operating environment

so that the operating junction temperature (T )

d o e s

n o t

e x c e e d t h e

m a x i m u m j u n c t i o n

t e m p e r a t u r e

( T

m a x ) .

T h e

t w o

m a i n

environmental variables that a designer can use

to improve thermal performance are air flow and

e x t e r n a l h e a t s i n k s . T h e p u r p o s e

o f t h i s

information is to aid the designer in determining

the proper operating environment for a linear

regulator that is operating at a specific power

level.

I n g e n e r a l , t h e m a x im u m e x p e c t e d p o w e r

(P (max)) consumed by a linear regulator is

computed as:

Where:

is the average input voltage.

is the average output voltage.

is the average output current.

is the quiescent current.

For most LDO regulators, the quiescent current is

insignificant compared to the average output

current; therefore, the term V

can be

neglected. The operating junction temperature is

computed by adding the ambient temperature (T )

and the increase in temperature due to the

regulator' s power dissipation. The temperature

rise is computed by multiplying the maximum

expected power dissipation by the sum of the

thermal resistances between the junction and the

case R

), the case to heatsink (R

), and the

heatsink to ambient (R

). Thermal resistances

are measures of how effectively an object

dissipates heat. Typically, the larger the device,

the more surface area available for power

dissipation so that the object’

s thermal resistance

will be lower.

External Capacitor Requirements

Regulator Protection

Thermal Information

I (avg)

O(avg)

(Q)

I(avg)

(Q)

(

Application Information

( )

(

) ( ) ( ) ( )

DMAX

I avg

O avg

I avg

= V

-V

×I

1.5A Low Dropout Voltage CMOS Regulator

06/2011 Rev2.2

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