參數(shù)資料
型號(hào)： LM4868LQ/NOPB
廠(chǎng)商： NATIONAL SEMICONDUCTOR CORP
元件分類(lèi)： 音頻／視頻放大
英文描述： 3 W, 2 CHANNEL, AUDIO AMPLIFIER, PQCC24
封裝： EXPOSED PAD, PLASTIC, LLP-24
文件頁(yè)數(shù)： 8/28頁(yè)
文件大?。?/td> 792K
代理商： LM4868LQ/NOPB
Application Information (Continued)
pop performance. The selection of bypass capacitor values,
especially C
B, depends on desired PSRR requirements,
click and pop performance (as explained in the section,
Proper Selection of External Components), system cost,
and size constraints.
MICROPOWER SHUTDOWN
The voltage applied to the SHUTDOWN pin controls the
LM4868’s shutdown function. Activate micropower shut-
down by applying V
DD to the SHUTDOWN pin. When active,
the LM4868’s micropower shutdown feature turns off the
amplifier’s bias circuitry, reducing the supply current. The
logic threshold is typically V
DD/2. The low 0.7A typical
shutdown current is achieved by applying a voltage that is as
near as V
DD as possible to the SHUTDOWN pin. A voltage
that is less than V
DD may increase the shutdown current.
Table 1 shows the logic signal levels that activate and deac-
tivate micropower shutdown and headphone amplifier op-
eration. To ensure that the output signal remains
transientfree, do not cycle the shutdown function
faster than 1Hz.
There are a few ways to control the micropower shutdown.
These include using a singlepole, single, throw switch, a
microprocessor, or a microcontroller. When using a switch,
connect an external 100k
pullup resistor between the
SHUTDOWN pin and V
DD. Connect the switch between the
SHUTDOWN pin and ground. Select normal amplifier opera-
tion by closing the switch. Opening the switch connects the
SHUTDOWN pin to V
DD through the pullup resistor, acti-
vating micropower shutdown. The switch and resistor guar-
antee that the SHUTDOWN pin will not float. This prevents
unwanted state changes. In a system with a microprocessor
or a microcontroller, use a digital output to apply the control
voltage to the SHUTDOWN pin. Driving the SHUTDOWN pin
with active circuitry eliminates the pull up resistor.
Truth Table for Logic Inputs
SHUTDOWN
PIN
HP-IN
PIN
MUX CHANNEL
INPUT SELECT
OPERATIONAL MODE (MUX
INPUTCHANNEL #)
Logic Low
= OUTB signal
Logic Low
Bridged amplifiers (1)
Logic Low
= OUTB signal
Logic High
Bridged amplifiers (2)
Logic Low
≠ OUTB signal
Logic Low
Single-ended amplifiers (1)
Logic Low
≠ OUTB signal
Logic High
Single-ended amplifiers (2)
Logic High
X
Micropower shutdown
HEADPHONE (SINGLE-ENDED) AMPLIFIER
OPERATION
An internal pullup circuit is connected to the HPIN (pin 20)
headphone amplifier control pin. When this pin is left uncon-
nected, V
DD is applied to the HPIN. This turns off Amp2B
and switches Amp2A’s input signal from an audio signal to
the V
DD/2 voltage present on pin 14. The result is muted
bridge-connected loads. Quiescent current consumption is
reduced when the IC is in this singleended mode.
Figure 8 shows the implementation of the LM4868’s head-
phone control function. An internal comparator with a nomi-
nal 400mV offset monitors the signal present at the OUTB
output. It compares this signal against the signal applied to
the HPIN pin. When these signals are equal, as is the case
when a BTL is connected to the amplifier, the comparator
forces the LM4868 to maintain bridgedamplifier operation.
When the HPIN pin is externally floated, such as when
headphones are connected to the jack shown in Figure 8,
and internal pullup forces V
DD on the internal comparator’s
HPIN inputs. This changes the comparator’s output state
and enables the headphone function: it turns off Amp2B,
switches Amp2A’s input signal from an audio signal to the
V
DD/2
voltage
present
on
pin
14,
and
mutes
the
bridge-connected loads. Amp1A and Amp1B drive the head-
phones.
Figure 8 also shows the suggested headphone jack electri-
cal connections. The jack is designed to mate with a
threewire plug. The plug’s tip and ring should each carry
one of the two stereo output signals, whereas the sleeve
provides the return to Amp2A. A headphone jack with one
control pin contact is sufficient to drive the HPIN pin when
connecting headphones.
A switch can replace the headphone jack contact pin. When
a switch shorts the HPIN pin to V
DD, bridgeconnected
speakers are muted and Amp1A and Amp2A drive a pair of
headphones. When a switch shorts the HPIN pin to GND,
the LM4868 operates in bridge mode. If headphone drive is
not needed, short the HPIN pin to the OUTB pin.
Figure 7 shows an optional resistor connected between the
amplifier output that drives the headphone jack sleeve and
ground. This resistor provides a ground path that supressed
power supply hum. This hum may occur in applications such
as notebook computers in a shutdown condition and con-
nected to an external powered speaker. The resistor’s 100
value is a suggested starting point. Its final value must be
determined based on the tradeoff between the amount of
noise suppression that may be needed and minimizing the
additional current drawn by the resistor (25mA for a 100
resistor and a 5V supply).
ESD Protection
As stated in the Absolute Maximum Ratings, pin 28 on the
MT and MH packages have a maximum ESD susceptibility
rating of 8000V. For higher ESD voltages, the addition of a
PCDN042 dual transil (from California Micro Devices), as
shown in Figure 7, will provide additional protection.
LM4868
www.national.com
16
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參數(shù)描述
LM4868MT 制造商:NSC 制造商全稱(chēng):National Semiconductor 功能描述:Output-Transient-Free Dual 2.1W Audio Amplifier Plus No Coupling Capacitor Stereo Headphone Function
LM4868MT/NOPB 功能描述:IC AMP AUDIO PWR 3W AB 20TSSOP RoHS:是 類(lèi)別:集成電路 (IC) >> 線(xiàn)性 - 音頻放大器 系列:Boomer® 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:2,500 系列:DirectDrive® 類(lèi)型:H 類(lèi) 輸出類(lèi)型:耳機(jī)，2-通道（立體聲） 在某負(fù)載時(shí)最大輸出功率 x 通道數(shù)量:35mW x 2 @ 16 歐姆 電源電壓:1.62 V ~ 1.98 V 特點(diǎn):I²C，麥克風(fēng)，靜音，短路保護(hù)，音量控制 安裝類(lèi)型:表面貼裝 供應(yīng)商設(shè)備封裝:25-WLP（2.09x2.09） 封裝/外殼:25-WFBGA，WLCSP 包裝:帶卷 (TR)
LM4868MTE 制造商:NSC 制造商全稱(chēng):National Semiconductor 功能描述:Output-Transient-Free Dual 2.1W Audio Amplifier Plus No Coupling Capacitor Stereo Headphone Function
LM4868MTE/NOPB 功能描述:IC AMP AUDIO PWR 3W AB 20TSSOP RoHS:是 類(lèi)別:集成電路 (IC) >> 線(xiàn)性 - 音頻放大器 系列:Boomer® 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:2,500 系列:DirectDrive® 類(lèi)型:H 類(lèi) 輸出類(lèi)型:耳機(jī)，2-通道（立體聲） 在某負(fù)載時(shí)最大輸出功率 x 通道數(shù)量:35mW x 2 @ 16 歐姆 電源電壓:1.62 V ~ 1.98 V 特點(diǎn):I²C，麥克風(fēng)，靜音，短路保護(hù)，音量控制 安裝類(lèi)型:表面貼裝 供應(yīng)商設(shè)備封裝:25-WLP（2.09x2.09） 封裝/外殼:25-WFBGA，WLCSP 包裝:帶卷 (TR)
LM4869 制造商:NSC 制造商全稱(chēng):National Semiconductor 功能描述:1.9W Differential Input, BTL Output Stereo Audio Amplifier with Selectable Gain and Shutdown
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