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參數(shù)資料
| 型號： | LM4663MT/NOPB |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 音頻／視頻放大 |
| 英文描述： | 2.1 W, 2 CHANNEL, AUDIO AMPLIFIER, PDSO24 |
| 封裝： | TSSOP-24 |
| 文件頁數(shù)： | 8/11頁 |
| 文件大?。?/td> | 1007K |
| 代理商： | LM4663MT/NOPB |
Applications Information (Continued)
present in the Class D output waveform. This energy would
be dissipated in the load impedance’s resistive component,
which diminishes efficiency.
BYPASS PIN CAPACITOR
In order to achieve the largest unclipped output voltage
swing, a DC reference voltage for the circuit is derived
internally by a resistor divider from the power supply voltage.
To reduce sensitivity to audio frequency variations on the
reference voltage, a de-coupling capacitor is recommended
between the BYPASS pin and the best available AC ground
reference. This is typically the shield connection from the
signal source. A poor choice is the power ground because
considerable current flows from the LM4663 through pins
4,8,17, and 21 to the power supply return. This current is rich
in harmonic frequencies related to the input audio frequency.
These harmonics can easily couple into the signal path by
sharing power ground conductors with the bypass capacitor
connection. The result is increased THD.
MINIMUM LOAD RESISTANCE
As specified in the Absolute Maximum Ratings, the minimum
load resistance supported by the LM4663 at the output of the
filters is 2.5 Ohms. Loads (usually loudspeakers) should be
tested over the audio band to determine whether or not there
are resonant points of diminshed impedance less than this
limit.
OUTPUT FILTER COMPONENTS
Table 2 shows suggested standard values of the capacitor
(C) and the inductor (L) used in Figure 1’s output filter for 4
and 8
loads. The bandwidth for each case is typically
18kHz.
TABLE 2. Output filter component values for different
load resistance.
Load Resistance (
) Capacitor C (F) Inductor L (H)
42
22
81
44
SHORT CIRCUIT TOLERANCE
The LM4663, when used in the recommended application
circuit, is tolerant of limited duration short circuit connections
between the filtered positive and negative outputs. Shorts
from either output to ground or supply voltage, or from the
unfiltered outputs to any other low impedance node can
result in permanent damage to the IC.
START-UP CURRENT
The LM4663 exhibits abnormally high quiescent current
drain when the supply voltage is below the specified operat-
ing range of 4.5 to 5.5V. It is, therefore, recommended that
the IC be initially powered up in the shutdown mode (SD =
V
DD). Normal application of power from laboratory bench
supplies is not usually a problem unless the current limit of
the supply is set too low (<1A); however, some applications
have a much lower current capability (such as USB applica-
tions). In these cases power must be applied with shutdown
asserted and switched to the operating mode after power is
present and settled. An external circuit that provides this
condition automatically is given in Figure 2, and is recom-
mended for those current-critical applications.
PRINTED CIRCUIT BOARD LAYOUT
Figures 3 through 7 show the layout of a recommended
four-layer PC board that is optimized for the LM4663 and
associated external components. This layout emphasizes
short connections between the power reservoir capacitors
near the power amp outputs and their associated pins. Short
connections reduce inductance and EMI radiation from the
output switching currents. Also, the distance from the switch-
ing outputs to the filter inductors is similarly minimized to
reduce radiated noise. Table 4 is the recommended circuit’s
bill-of-materials (BOM). Figure 8 is a photograph of the
recommended four-layer PC board.
The board is designed for use with an external 5V supply, 4
speakers, and 32
headphones. Apply the supply voltage to
the V
DD pad and ground to the GND pad. Connect the left
channel speaker between the Lout+ and Lout pads and the
right channel speaker between the Rout+ and Rout pads.
Connect the left and right headphone speakers to the HPL
and HPR pads, respectively. The board has two sets of HPL
and HPR pads. Use the set found across the top edge for a
headphone jack like that shown in Figure 1. The other set
found along the right edge can be used for a three terminal
headphone jack. Ensure that a speaker’s + terminal is con-
nected to an amplifier’s + output. This preserves the phase
relationship between the left and right channels.
The board accepts two stereo inputs. Apply channel 1’s right
and left input signals to the Rin1 and Lin1 pads, respectively.
Apply channel 2’s right and left input signals to the Rin2 and
Lin2 pads, respectively.
The board’s bottom edge has seven jumpers. From left to
right, these jumpers select micropower shutdown, input
channel, headphone amplifier, Class D amplifier, and head-
phone amplifier when plugging in headphones. Table 3 is a
guide for selecting the various functions.
TABLE 3. These are the functions selected by the jumpers on the recommended PC board.
Jumper
Function
SD-L
Shorting selects normal operation.
SD-H Jumper is open.
SD-H
Shorting activates shutdown: micropower operation.
SD-L Jumper is open.
INSEL-L
Shorting selects stereo input 2.
INSEL-H Jumper is open.
INSEL-H
Shorting selects stereo input 1.
INSEL-L Jumper is open.
LM4663
www.national.com
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相關PDF資料 |
PDF描述 |
|---|---|
| LM4663MTX/NOPB | 2.1 W, 2 CHANNEL, AUDIO AMPLIFIER, PDSO24 |
| LM4664ITL/NOPB | 1.1 W, 1 CHANNEL, AUDIO AMPLIFIER, PBGA9 |
| LM4664ITLX/NOPB | 1.1 W, 1 CHANNEL, AUDIO AMPLIFIER, PBGA9 |
| LM4665MM/NOPB | 1 W, 1 CHANNEL, AUDIO AMPLIFIER, PDSO10 |
| LM4665MMX/NOPB | 1 W, 1 CHANNEL, AUDIO AMPLIFIER, PDSO10 |
相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| LM4663MTX | 制造商:Rochester Electronics LLC 功能描述: 制造商:Texas Instruments 功能描述: |
| LM4664 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Filterless High Efficiency 1.1W Switching Audio Amplifier |
| LM4664ITL | 制造商:Texas Instruments 功能描述:AMP FILTERLESS CLASS-A 1.1W 4664 |
| LM4665 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Filterless High Efficiency 1W Switching Audio Amplifier |
| LM4665 WAF | 制造商:Texas Instruments 功能描述: |
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