APL5331 datasheet(10/20 Pages) ANPEC

10 / 20 page

 ANPEC Electronics Corp.

Rev. A.8 - Oct., 2003

APL5331

www.anpec.com.tw

Application Information

General

The APL5331 is a linear regulator and is capable of

sourcing or sinking current up to 3A. The APL5331

has fast transient response, accurate output voltage

(small voltage offset, load regulation), active-low shut-

down control and fault protections (current-limit, ther-

mal shutdown). The APL5331 is available in several

packages to meet different of power dissipation in

requirement various applications.

Output Voltage Regulation

The output voltage at VOUT pin tracks the reference

voltage applied at VREF pin. Two internal NPN pass

transistors controlled by separate high bandwidth er-

ror amplifiers regulate the output voltage by sourcing

current from VIN pin or sinking current to GND pin.

The base currents of the pass transistors are pro-

vided by VCNTL pin. An internal kelvin sensing

scheme use at the VOUT pin for perfect load regula-

tion at various load current. To prevent the two pass

transistors from shoot-through, a small voltage offset

is created between the positive inputs of the two error

amplifiers. This results in higher output voltage while

the regulator sinks light or heavy load current. Since

the APL5331 exhibits very fast load transient

response, lesser amount of capacitors can be use.

In addition, capacitors with high ESR can also be

use.

Shutdown and Soft-Start

The VREF pin is a dual-function input pin, acting as

reference input and shutdown control input. Apply-

ing and holding a voltage below 0.35V(typ.) to VREF

pin shuts down the output of the regulator. An NPN

transistor or N-channel MOSFET is used to pull down

the VREF while applying a “high” signal to turn on the

transistor. When shutdown function is active, the

two pass transistors are turned off and the imped-

ance of the VOUT is about 10M

Ω (typ.), sourcing or

sinking no current. When release the VREF pin, the

current through the resistor divider charges the soft-

start capacitor to initiate a soft-start cycle. The output

voltage tracks the rising VREF. The soft start process

limits the input surge current.

Thermal Shutdown

An thermal shutdown circuit limits the junction tem-

perature of the APL5331. When the junction tem-

perature exceeds TJ= +150oC, a thermal sensor turns

off both pass transistors, allowing the device to cool

down. The regulator starts to regulate again after the

junction temperature reduces by 40oC, resulting in a

pulsed output during continuous thermal overload

conditions. The thermal limit designed with a 40oC

hysteresis lowers the average TJ during continuous

thermal overload conditions, extend life time of

APL5331.

Current Limit

The APL5331 monitors sourcing and sinking current,

and limits the maximum output current to prevent dam-

ages during overload or short-circuit, To increase

the input voltage of VIN or VCNTL will get higher

current-limit points.

APL5331 Datasheet(PDF) 10 Page - Anpec Electronics Coropration

APL5331 Datasheet(HTML) 10 Page - Anpec Electronics Coropration

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Datasheet Download

Link URL