APL5331 datasheet(13/23 Pages) ANPEC

13 / 23 page

Rev. B.4 - Mar., 2008

APL5331

www.anpec.com.tw

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

shutdown control and fault protections (current-limit,

thermal 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

error 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 provided

by VCNTL pin. An internal kelvin sensing scheme

senses the output voltage on VOUT pin for perfect

Application Information

load regulation. To prevent 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

load current. Since the APL5331 exhibits very fast load

transient response, lesser amount of capacitors can be

used. In addition, capacitors with high ESR can also

be used.

Current Limit

The APL5331 monitors sourcing and sinking output

currents, and limits the maximum output currents to

prevent damages during overload or short-circuit

condition. To increase the voltage across the internal

pass transistors will get higher current-limit points.

Shutdown and Soft-Start

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

reference input and shutdown control input. Applying

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 voltage while applying a “high” signal to

turn on the transistor. When shutdown function is

active, both pass transistors are turned off and the

impedance 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 process

which controls the rise rate of the output voltage and

limits the input surge current.

Thermal Shutdown

A thermal shutdown circuit lim its the junction

temperature of the APL5331. When the junction

temperature exceeds +183oC, 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, and extends lifetime of

APL5331.

Power Inputs

It's not necessary to pay attention to the sequencing

of the input voltages on VIN and VCNTL pins. However,

do not apply a voltage to VOUT when the VCNTL

voltage is not present. This reason is that the internal

parasitic diodes connected from VOUT to VIN and from

VOUT to VCNTL will be forward biased. When the VIN

input voltage is not present, the APL5331 can only

source few current up to 100mA to output. In the same

condition, the APL5331 keeps same capability of

sinking output current up to 3A.

Shutdown and Soft-Start (Cont.)

APL5331 数据表(PDF) 13 Page - Anpec Electronics Coropration

APL5331 数据表(HTML) 13 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 21 22 23

数据表下载