The JTM145 is a high-efficiency, filterless Class-D audio po

1.产品概述         2.产品特点
3.应用范围       4.下载产品资料PDF文档
5.产品封装图                     6.电路原理图
7.功能概述       8.相关产品

一,产品概述(General Description)
        The JTM145 is a high-efficiency, filterless Class-D audio power amplifier with
automatic level control (ALC). It operates from 2.7V to 5.5V supply.When powered
with 5V supply voltage, the JTM145 is capable of delivering 3.2W into 4Ω load or
1.8W into 8Ω load with 10% THD+D.The JTM145 features ALC on the audio output
signals, which detects the output clipping caused by the over-level input signal and automatically adjusts the voltage gain of the amplifier to eliminate the clipping while maintaining the maximally-allowed dynamic range of the audio output signals. The
ALC also eliminates the output clipping due to low battery supply voltage.As a Class-D
power amplifier, the ft2045 features high efficiency (up to 88%) and high PSRR (70dB
at 217Hz), which make the device ideal for use in battery-powered portable devices. It
also features minimized click-and-pop noise during turn-on and turn-off transitions.

二.产品特点(Features)
Filterless Class-D operation
   Automatic level control to eliminate output clipping
High efficiency up to 90%
Maximum output power at 5V supply (ALC Off)
             3.2W (4Ω load, 10% THD+N)
             1.8W (8Ω load, 10% THD+N)
Constant output power at 5V supply (ALC On)
            2.4W (4Ω load, THD+N < 0.6%)
            1.35W (8Ω load, THD+N < 0.5%)
Constant output power at 3.6V supply (ALC On)
            1.2W (4Ω load, THD+N < 0.6%)
             0.7W (8Ω load, THD+N < 0.5%)
Low THD+N < 0.05%
            (VDD=3.6V, f=1kHz, RL=8Ω, PO=0.5W)
Low quiescent current: 2.2mA @ VDD=3.6V
Low shutdown current < 0.1µA
High PSRR: 75dB @ 217Hz
Short-circuit & thermal overload protection
Fast startup time: 4ms
Available in MSOP-8L package

三,应用范围 (Applications)
Cellular handsets
Portable navigation devices
Multimedia internet devices

四.下载产品资料PDF文档

jtm145

五,产品封装图 (Package)

SYMBOL	MSOP-8L	DESCRIPTION
CTRL	1	Mode control input for ALC and Shutdown.
VREF	2	Analog reference at VDD/2, the common-mode bias for audio inputs.
INP	3	Positive audio input terminal.
INN	4	Negative audio input terminal.
VON	5	Negative BTL audio output terminal.
VDD	6	Power supply.
GND	7	Power ground.
VOP	8	Positive BTL audio output terminal.

六.电路原理图

七,功能概述

APPLICATIONS INFORMATION

The JTM145 is a high-efficiency, filterless Class-D audio power amplifier with automatic level control

(ALC). It operates from 2.7V to 5.5V supply. When powered with 5V supply voltage, the JTM145 is
capable of delivering 3.2W into 4Ω load or 1.8W into 8Ω load, with 10% THD+N. When operated in ALC
mode with 5V supply voltage, the JTM145 is capable of delivering 2.4W into 4Ω load or 1.35W into 8Ω
load, with THD+D less than 0.5%.

The JTM145 features ALC on the audio output signals, which detects the output clipping caused by the
over-level input signal and automatically adjusts the voltage gain of the amplifier to eliminate the clipping
while maintaining the maximally-allowed dynamic range of the audio output signals. The ALC also
eliminates the output clipping due to low battery supply voltage.

In addition, the JTM145 features a filterless PWM modulator that eliminates the need for an external LC
filter, therefore reducing the number of external components, the PCB board space, and the system cost.
In this manner, the power efficiency is also improved.

As specifically designed for portable applications, the JTM145 incorporates a shutdown mode to minimize
the power consumption by holding the CTRL pin to ground. It also includes comprehensive protection
features against various operating faults such as over-current, short-circuit, over-temperature, or
under-voltage for a safe and reliable operation.

AUTOMATIC LEVEL CONTROL (ALC)

The automatic level control is to maintain the audio output signals for a maximum voltage swing without

distortion when an excessive input that may cause output clipping is applied. With the ALC function, the
JTM145 lowers the voltage gain of the amplifier to an appropriate value such that the clipping at the
outputs is eliminated. It also eliminates the clipping of the output signal due to the reduction of the
power-supply voltage.

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