Preliminary Datasheet

LP3983H

LP3983H–00 Version 1.0 Aug.-2014

www.lowpowersemi.com

Page 7 of 10

Applications Information

L

ike any low-dropout regulator, the external capacitors

used with the LP3983H must be carefully selected for

regulator stability and performance. Using a capacitor

whose value is > 1µF on the LP3983H 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 LP3983H 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 LP3983H output

ensures stability. The LP3983H still works well with output

capacitor of other types due to the wide stable ESR range.

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

clean analog ground.

Start-up Function Enable Function

The LP3983H 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 1.4 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

LP3983H

have

a

quick-discharge function. If the enable function is not

keep the LDO regulator in a continuously on state.

Feedback Capacitor and Bypass

Capacitor

For adjustable version, connecting a 22pF between

output pin and FB pin significantly reduces output voltage

ripple, it is critical that the capacitor connection should be

direct and PCB traces should be as short as possible.

For LP3983HB6F08/9, connecting a 10nF between the

BP pin and GND pin significantly reduces noise on the

regulator output, it is critical that the capacitor connection

between the BP pin and GND pin be direct and PCB

traces should be as short as possible. There is a

relationship between the bypass capacitor value and the

LDO regulator turn on time. DC leakage on this pin can

affect the LDO regulator output noise and voltage

regulation performance.

Thermal Considerations

Thermal protection limits power dissipation in LP3983H.

When the operation junction temperature exceeds 165°C,

the OTP circuit starts the thermal shutdown function turn

the pass element off. The pass element turns 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:

The maximum power dissipation depends on the thermal

resistance of IC package, PCB layout, the rate of