Preliminary Datasheet

LP2201

LP2201 – Ver. 1.2Datasheet

Jul.-2008

Page 6 of 8

Applications Information

L

ike any low-dropout regulator, the external capacitors

used with the LP2201 must be carefully selected for

regulator stability and performance. Using a capacitor

whose value is > 1µF on the LP2201 input and the

amount of capacitance can be increased without limit.

The input capacitor must be located a distance of not

more than 0.5 inch from the input pin of the IC and

returned to a clean analog ground. Any good quality

ceramic or tantalum can be used for this capacitor. The

capacitor with larger value and lower ESR (equivalent

series

resistance)

provides

better

PSRR

and

line-transient response. The output capacitor must meet

both requirements for minimum amount of capacitance

and ESR in all LDOs application. The LP2201 is designed

specifically to work with low ESR ceramic output

capacitor in space-saving and performance consideration.

Using a ceramic capacitor whose value is at least 1µF

with ESR is > 25mΩ on the LP2201 output ensures

stability. The LP2201 still works well with output capacitor

of other types due to the wide stable ESR range. Figure 1

shows the curves of allowable ESR range as a function of

load current for various output capacitor values. Output

capacitor of larger capacitance can reduce noise and

improve load transient response, stability, and PSRR.

The output capacitor should be located not more than 0.5

inch from the VOUT pin of the LP2201 and returned to a

clean analog ground.

Start-up Function Enable Function

The LP2201 features an LDO regulator enable/disable

function. To assure the LDO regulator will switch on, the

EN turn on control level must be greater than 1.2 volts.

The LDO regulator will go into the shutdown mode when

the voltage on the EN pin falls below 0.4 volts. For to

protecting

the

system,

the

LP2201

have

a

quick-discharge function. If the enable function is not

needed in a specific application, it may be tied to VIN to

keep the LDO regulator in a continuously on state.

Thermal Considerations

Thermal protection limits power dissipation in LP2201.

When the operation junction temperature exceeds 165°C,

the OTP circuit starts the thermal shutdown function turn

the pass element off. The pass element turn on again

after the junction temperature cools by 30°C. For continue

operation, do not exceed absolute maximum operation

junction temperature 125°C.

The power dissipation definition in device is :

PD = (VIN−VOUT) x IOUT + VIN x IQ

The maximum power dissipation depends on the thermal

resistance of IC package, PCB layout, the rate of

surroundings airflow and temperature difference between

junction to ambient.

The maximum power dissipation can be calculated by

following formula :

PD(MAX) = ( TJ(MAX) − TA ) /θJA

Where TJ(MAX) is the maximum operation junction