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Application Information (Continued)
present on the internal amplifier’s input may change. This
change can slew at a rate that may produce audible voltage
transients or clicks in the amplifier’s output signal. Using the
MUX to select between two vastly dissimilar gains is a typical
transient-producing situation. As the MUX is switched, an
audible click may occur as the gain suddenly changes.
PIN OUT COMPATIBILITY WITH THE LM4863
The LM4867 pin out was designed to simplify replacing the
LM4863: except for the four Pins(-IN A
2, MUX CTRL, -IN B2,
and NC) that implement the LM4867’s extra functionality, the
LM4867MT/MTE and LM4863MT/MTE pin outs match.
(Note 19)
Note 19: If the LM4867 replaces an LM4863 and the input MUX circuitry is
not being used, the LM4867 MUX CTRL pin must be tied to VDD or GND and
the unused MUX inputs must be connected to GND.
EXPOSED-DAP MOUNTING CONSIDERATIONS
The LM4867’s exposed-DAP (die attach paddle) packages
(MTE and LQ) provide a low thermal resistance between the
die and the PCB to which the part is mounted and soldered.
This allows rapid heat transfer from the die to the surround-
ing PCB copper area heatsink, copper traces, ground plane,
and finally, surrounding air. The result is a low voltage audio
power amplifier that produces 2.4W dissipation in a 4
load
at
≤ 1% THD+N and over 3W in a 3 load at 10% THD+N.
This high power is achieved through careful consideration of
necessary thermal design. Failing to optimize thermal design
may compromise the LM4867’s high power performance and
activate unwanted, though necessary, thermal shutdown
protection.
The MTE and LQ packages must have their DAPs soldered
to a copper pad on the PCB. The DAP’s PCB copper pad is
then, ideally, connected to a large plane of continuous un-
broken copper. This plane forms a thermal mass, heat sink,
and radiation area. Place the heat sink area on either outside
plane in the case of a two-sided or multi-layer PCB. (The
heat sink area can also be placed on an inner layer of a
multi-layer board. The thermal resistance, however, will be
higher.) Connect the DAP copper pad to the inner layer or
backside copper heat sink area with 32 (4 X 8) (MTE) or 6 (3
X 2) (LQ) vias. The via diameter should be 0.012in - 0.013in
with a 1.27mm pitch. Ensure efficient thermal conductivity by
plugging and tenting the vias with plating and solder mask,
respectively.
Best thermal performance is achieved with the largest prac-
tical copper heat sink area. If the heatsink and amplifier
share the same PCB layer, a nominal 2.5in
2 (min) area is
necessary for 5V operation with a 4
load. Heatsink areas
not placed on the same PCB layer as the LM4867 should be
5in
2 (min) for the same supply voltage and load resistance.
The last two area recommendations apply for 25C ambient
temperature. Increase the area to compensate for ambient
temperatures above 25C. In systems using cooling fans, the
LM4867MTE can take advantage of forced air cooling. With
an air flow rate of 450 linear-feet per minute and a 2.5in
2
exposed copper or 5.0in
2 inner layer copper plane heatsink,
the LM4867MTE can continuously drive a 3
load to full
power. The LM4867LQ achieves the same output power
level without forced-air cooling. In all circumstances and
under all conditions, the junction temperature must be held
below 150C to prevent activating the LM4867’s thermal
shutdown protection. The LM4867’s power de-rating curve in
the Typical Performance Characteristics shows the maxi-
mum power dissipation versus temperature. Example PCB
layouts for the exposed-DAP TSSOP and LQ packages are
shown in the Demonstration Board Layout section. Further
detailed and specific information concerning PCB layout and
fabrication and mounting an LQ (LLP) is found in National
Semiconductor’s AN1187.
20001339
FIGURE 6. As configured, connecting headphones to this jack automatically selects the stereo headphone amplifier
and, with the additional NC switch, changes MUX channels (Network 2 in Figure 5 )
LM4867
www.national.com
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相关代理商/技术参数
LM4867MT 制造商:NSC 制造商全称:National Semiconductor 功能描述:Output-Transient-Free Dual 2.1W Audio Amplifier Plus No Coupling Capacitor Stereo Headphone Function
LM4867MT NOPB 制造商:Texas Instruments 功能描述:Audio Amp Headphone/Speaker 2-CH Stereo 1.5W Class-AB 20-Pin TSSOP Rail
LM4867MT/NOPB 功能描述:IC AMP AUDIO PWR 3W AB 20TSSOP RoHS:是 类别:集成电路 (IC) >> 线性 - 音頻放大器 系列:Boomer® 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:DirectDrive® 类型:H 类 输出类型:耳机，2-通道（立体声） 在某负载时最大输出功率 x 通道数量:35mW x 2 @ 16 欧姆 电源电压:1.62 V ~ 1.98 V 特点:I²C，麦克风，静音，短路保护，音量控制 安装类型:表面贴装 供应商设备封装:25-WLP（2.09x2.09） 封装/外壳:25-WFBGA，WLCSP 包装:带卷 (TR)
LM4867MTE 制造商:Texas Instruments 功能描述:Audio Amp Headphone/Speaker 2-CH Stereo 3W Class-AB 20-Pin TSSOP EP Rail
LM4867MTE/NOPB 功能描述:IC AMP AUDIO PWR 3W AB 20TSSOP RoHS:是 类别:集成电路 (IC) >> 线性 - 音頻放大器 系列:Boomer® 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:DirectDrive® 类型:H 类 输出类型:耳机，2-通道（立体声） 在某负载时最大输出功率 x 通道数量:35mW x 2 @ 16 欧姆 电源电压:1.62 V ~ 1.98 V 特点:I²C，麦克风，静音，短路保护，音量控制 安装类型:表面贴装 供应商设备封装:25-WLP（2.09x2.09） 封装/外壳:25-WFBGA，WLCSP 包装:带卷 (TR)
LM4867MTEX 制造商:National Semiconductor Corporation 功能描述:Audio Amplifier Circuit, Dual, 20 Pin, Plastic, TSSOP
LM4867MTEX/NOPB 功能描述:IC AMP AUDIO PWR 3W AB 20TSSOP RoHS:是 类别:集成电路 (IC) >> 线性 - 音頻放大器 系列:Boomer® 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:DirectDrive® 类型:H 类 输出类型:耳机，2-通道（立体声） 在某负载时最大输出功率 x 通道数量:35mW x 2 @ 16 欧姆 电源电压:1.62 V ~ 1.98 V 特点:I²C，麦克风，静音，短路保护，音量控制 安装类型:表面贴装 供应商设备封装:25-WLP（2.09x2.09） 封装/外壳:25-WFBGA，WLCSP 包装:带卷 (TR)
LM4867MTX/NOPB 功能描述:IC AMP AUDIO PWR 3W AB 20TSSOP RoHS:是 类别:集成电路 (IC) >> 线性 - 音頻放大器 系列:Boomer® 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:DirectDrive® 类型:H 类 输出类型:耳机，2-通道（立体声） 在某负载时最大输出功率 x 通道数量:35mW x 2 @ 16 欧姆 电源电压:1.62 V ~ 1.98 V 特点:I²C，麦克风，静音，短路保护，音量控制 安装类型:表面贴装 供应商设备封装:25-WLP（2.09x2.09） 封装/外壳:25-WFBGA，WLCSP 包装:带卷 (TR)