APL5332K データシートの表示（PDF） - Anpec Electronics

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APL5332K

CMOS LDO with Source-Sink & Output Selection Functions

Anpec Electronics 

APL5332

Functional Description

General

APL5332 is a source-sink linear regulator designed

for motherboard front side bus. The device can supply

loads from -1A to 2A in either fixed or adjustable volt-

age mode. APL5332 has a 0.8V reference, an error

amplifier, two pass transistors, fixed voltage selection,

an internal feedback resistor-divider, soft-start control

and fault protections(current-limit and thermal

shutdown). The output voltage is either 1.225V or 1.

45V selected by the BS pin when fixed voltage mode

is active by setting FB=VIN. When the FB is con-

nected with a feedback resistor-divider, the IC oper-

ates in adjustable voltage mode and the voltage of FB

is regulated to 0.8V. In the mode, the input of BS pin

is ignored. APL5332 is available in the SOP, SOP-8-

P, and TO-252-5 packages to meet different power

dissipation applications.

Output Voltage Regulation

The error amplifier working with the temperature-com-

pensated 0.8V reference and the two pass transistors

(high-side and low-side) regulates the output to the

preset voltage. The error amplifier compares the refer-

ence with the feedback voltage and amplifies the dif-

ference to drive one of the pass transistors. The high-

side pass transistor provides current from VIN to VOUT

and increases the output voltage when the feedback

voltage is lower than the reference. The low-side pass

transistor provides current from VOUT to GND and de-

creases the output voltage when the feedback voltage is

higher than the reference. The two pass transistors are

well controlled by the error amplifier and prevented short-

through conditions. An internal output voltage sense pad

is bonded to the VOUT pin for perfect load regulation in

fixed voltage mode.

Current Limit

The APL5332 monitors the sourcing or sinking cur-

rents and limits the maximum output current to pre-

vent damages during overload or short-circuit

conditions.

Power-On-Reset and Soft-Start

A Power-On-Reset circuit monitors input voltage of

the VIN pin and prevents wrong logic controls. When

the input voltage rises up more than the Power-On-

Reset threshold voltage, the device starts to output

current. Therefore, a soft-start circuit which controls

the reference voltage to rise up is required, limiting

surge input currents. The typical soft-start interval is

about 1mS.

Thermal Shutdown

A thermal shutdown circuit limits the junction tem-

perature of the APL5332. When the junction tempera-

ture exceeds +150oC, a thermal sensor turns off the

both pass transistors, allowing the device to cool

down. The regulator starts to regulate again after the

junction temperature cools by 25oC, resulting in a

pulsed output during continuous thermal overload

conditions. The thermal shutdown designed with a 25oC

hysteresis lowers the average junction temperature

during continuous thermal overload conditions, extend-

ing life time of APL5332.

For normal operation, device power dissipation should

be externally limited so that junction temperatures will

not exceed +125oC.

Copyright  ANPEC Electronics Corp.

8

Rev. A.3 - Oct., 2003

www.anpec.com.tw

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