RT9013A-33GY Просмотр технического описания (PDF) - Richtek Technology

Номер в каталоге

Компоненты Описание

производитель

RT9013A-33GY

120mA, Low Dropout, Low Noise Ultra-Fast Without Bypass Capacitor CMOS LDO Regulator

Richtek Technology 

RT9013A

Applications Information

Like any low-dropout regulator, the external capacitors used

with the RT9013A must be carefully selected for regulator

stability and performance. Using a capacitor whose value

is > 1uF / X7R on the RT9013A 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 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 RT9013A 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 1uF with ESR is > 20mΩ on the

RT9013A output ensures stability. The RT9013A 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 RT9013A

and returned to a clean analog ground.

Region of Stable COUT ESR vs. Load Current

100

Unstable Range

10

1

Stable Range

0.1

0.01

0.001

VIN = 5V

CIN = COUT = 1uF/X7R

Unstable Range

0

100

200

300

400

500

Load Current (mA)

Figure 1

Enable

The RT9013A goes into sleep mode when the EN pin is in

a logic low condition. During this condition, the RT9013A

has an EN pin to turn on or turn off regulator, When the EN

pin is logic hight, the regulator will be turned on. The supply

current to 0.7uA typical. The EN pin may be directly tied

to VIN to keep the part on. The Enable input is CMOS

logic and cannot be left floating.

PSRR

The power supply rejection ratio (PSRR) is defined as the

gain from the input to output divided by the gain from the

supply to the output. The PSRR is found to be

PSRR

=

20

×

log⎜⎛

⎝

ΔGain Error

ΔSupply

⎟⎞

⎠

Note that when heavy load measuring, Δsupply will cause

Δtemperature. And Δtemperature will cause Δoutput

voltage. So the heavy load PSRR measuring is include

temperature effect.

Current limit

The RT9013A contains an independent current limiter, which

monitors and controls the pass transistor's gate voltage,

limiting the output current to 0.2A (typ.). The output can

be shorted to ground indefinitely without damaging the part.

Thermal Considerations

Thermal protection limits power dissipation in RT9013A.

When the operation junction temperature exceeds 170°C,

the OTP circuit starts the thermal shutdown function and

turns the pass element off. The pass element turn on again

after the junction temperature cools by 30°C.

For continuous 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

DS9013A-02 April 2011

www.richtek.com

7

Share Link: