LPA2164ASOF datasheet(10/15 Pages) POWER

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Preliminary Datasheet

LPA2164A

LPA2164A–00

Version 1.0 May.-2013

Email: marketing@lowpowersemi.com

www.lowpowersemi.com

Page 10 of 15

Applications Information(for Amplifier)

Maximum Gain

The LPA2164A has two internal amplifier stages.

The first stage's gain is externally configurable, while

the second stage's is internally fixed. The

closed-loop gain of the first stage is set by selecting

the ratio of Rf to Ri while the second stage's gain is

fixed at 2x.The output of amplifier serves as the input

to amplifier 2, thus the two amplifiers produce signals

identical in magnitude, but different in phase by 180°.

Consequently, the differential gain for the IC is

Av=20*log [2*(Rf/Ri)]

The LPA2164A sets maximum:

Rf= 280 k ±10%

Class-AB

Rf= 280 k ±10%

Class-D

Shutdown operation

In order to reduce power consumption while not in

use, the LPA2164A contains shutdown circuitry to

turn off the amplifier's bias circuitry. This shutdown

feature turns the amplifier off when logic high is

applied to the SD pin. By switching the SD pin

connected to high voltage, the LPA2164A supply

current draw will be minimized in idle mode.

Power supply decoupling

The LPA2164A is a high performance CMOS audio

amplifier that requires adequate power supply

decoupling to ensure the output THD and PSRR a

low as possible. Power supply decoupling affects low

frequency response. Optimum decoupling is

achieved by using two capacitors of different types

targeting to different types of noise on the power

supply leads. For higher frequency transients, spikes,

or digital hash on the line, a good low

equivalent-series-resistance

(ESR)

ceramic

capacitor, typically 1.0ì

F, works best, placing it as

close as possible to the device VDD terminal. For

filtering lower- frequency noise signals, a large

capacitor

20ì

(ceramic)

greater is

recommended, placing it near the audio power

amplifier.

Short Circuit Protection (SCP)

The LPA2164A has short circuit protection circuitry

on the outputs to prevent damage to the device when

output-to-output or output-to-GND short occurs.

When a short circuit is detected on the outputs, the

outputs are disabled immediately. If the short was

removed, the device activates again.

Over Temperature Protection

Thermal protection on the LPA2164A prevents the

device from damage when the internal die

temperature exceeds 150℃. There is a 15 degree

tolerance on this trip point from device to device.

Once the die temperature exceeds the thermal set

point, the device outputs are disabled. This is not a

latched fault. The thermal fault is cleared once the

temperature of the die is reduced by 30℃. This large

hysteresis will prevent motor boating sound well and

the device begins normal operation at this point

without external system intervention.

Analog Reference Bypass Capacitor (CBYP)

In addition to system cost and size, click and pop

performance is affected by the size of the input

coupling capacitor, CBYP. A larger input coupling

capacitor requires more charge to reach its quiescent

DC voltage (nominally 1/2 VDD). This charge comes

from the internal circuit via the feedback and is apt to

create pops upon device enable. Thus, by minimizing

the capacitor size based on necessary low frequency

response, turn-on pops can be minimized.

The Analog Reference Bypass Capacitor (CBYP) is

the most critical capacitor and serves several

important functions. During start-up or recovery from

shutdown mode, CBYP determines the rate at which

the amplifier starts up. The second function is to

reduce noise caused by the power supply coupling

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