APA2175O Просмотр технического описания (PDF) - Anpec Electronics

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APA2175O

Stereo Cap-Free Line Driver

Anpec Electronics 

APA2175

Function Description

Line Driver Operation

VOUT

Conventional Line Driver

VOUT

VDD

VDD/2

0

VDD

0

VSS

Cap-free Line Driver

Figure 1. Cap-free Line Driver’s Operation

Shutdown Function

In order to reduce power consumption while not in use,

the APA2175 contains two shutdown controllers to allow

either channel being independent and externally turns off

the amplifier bias circuitry. LSD controls the left channel

and RSD controls the right channel. This shutdown fea-

ture turns the amplifier off when logic low is placed on the

RSD and LSD pins for the APA2175. The trigger point be-

tween a logic high is 1.0V and logic low level is 0.35V. It is

recommended to switch between ground and the supply

voltage V to provide maximum device performance. By

DD

switching the both RSD and LSD pins to the low level, the

amplifier enters a low-consumption current circumstance,

charge pump is disabled, and I for the APA2175 is in

DD

shutdown mode. The charge pump is enabled once ei-

ther RSD or LSD pin is pulled to high. In normal operating,

the APA2175’s RSD and LSD pins should be pulled to a

high level to keep the IC out of the shutdown mode. The

RSD and LSD pins should be tied to a definite voltage to

avoid unwanted circumstance changes.

The APA2175’s line drivers use a charge pump to invert

the positive power supply (VDD) to negative power supply

(VSS), see figure1. The line drivers operate at this bipolar

power supply (VDD and VSS) and the outputs reference re-

fers to the ground. This feature eliminates the output ca-

pacitor that is using in conventional single-ended line

drive amplifier. Compare with the single power supply

amplifier, the power supply range has almost doubled.

Thermal Protection

The thermal protection circuit limits the junction tempera-

ture of the APA2175. When the junction temperature ex-

ceeds TJ=+150OC, a thermal sensor turns off the driver,

allowing the devices to cool. The thermal sensor allows

the driver to start-up after the junction temperature down

about 125OC. The thermal protection is designed with a

25OC hysteresis to lower the average T during continu-

J

ous thermal overload conditions, increasing lifetime of

the ICs.

Copyright © ANPEC Electronics Corp.

11

Rev. A.3 - Jul., 2010

www.anpec.com.tw

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