参数资料
型号: TS34119CSRL
元件分类: 音频/视频放大
英文描述: 2 CHANNEL, AUDIO AMPLIFIER, PDSO8
封装: ROHS COMPLIANT, SOIC-8
文件页数: 9/13页
文件大小: 742K
代理商: TS34119CSRL
TS34119
Low Power Audio Amplifier
5/13
Version: A07
Design Guideline
GENERAL
The TS34119 is a low power audio amplifier capable of low voltage operation (Vcc=2.0V minimum) such as that
encountered in line-powered speakerphones. The circuit provides a differential output (VO1-VO2) to the speaker to
maximize the available voltage swing at low voltages. The different gain is set by two external resistors. Pins FC1 and
FC2 allow controlling the amount of power supply and noise rejection, as well as providing alternate inputs to the
amplifiers. The CD pin permits powering down the IC for muting purposes and to conserve power.
AMPLIFIERS
Referring to the block diagram, the internal configuration consists of two identical operational amplifiers. Amplifier #1
has an open loop gain of ≥80Db (at f≤100Hz), and the closed loop gain is set by external resistor Rf and Rj. The
amplifier is unity gain stable, and has a unity gain frequency of approximately 1.5MHz. In order to adequately cover
the telephone voice band (300Hz to 3.4kHz), a maximum closed loop gain of 46dB is recommended. Amplifier #2 is
internally set to gain of –1.0 (0dB). The outputs of both amplifiers are capable of souring and sinking a peak current of
200mA.The outputs can typically swing to within ≈ 0.4V above ground, and to within≈1.3V below VCC, at the
maximum current. See Figure 18 and 19 for VOH and VOL curves. The output dc offset voltage (VO1-VO2) is
primarily a function of the feedback resistor (Rf), and secondarily due to the amplifiers’ input offset voltages. The input
offset voltage of the two amplifiers will generally be similar for a particular IC, and therefore nearly cancel each other
at the outputs. Amplifier #1’s bias current, however, flows out of Vin (pin 4) and through Rf, forcing VO1 to shift
negative by an amount equal to (Rf × IIB), Vo2 is shifted posited an equal amount. The output offset voltage, specified
in the Electrical Characteristics is measured with the feedback the feedback resistor shown in the Typical Application
Circuit, and therefore takes into account the bias current as wells internal offset voltages of the amplifiers. The bias
current is constant with respect to VCC.
FC1 AND FC2
Power supply rejection is provided by the capacitors (C1 and C2 in the typical Application Circuit) at FC1 and FC2. C2
is somewhat dominant at low frequencies, while C1 is dominant at high frequencies, as shown in the graphs of Figure
4 to 7. The required values of C1 and C2 depend on the conditions of each application. A line powered
speakerphone, for example, will require more filtering than a circuit powered by a well regulated power supply. The
amount of rejection is function of the capacitors, and the equivalent impedance looking into FC1 and FC2 (listed in the
Electrical Characteristics as RFC1 and RFC2). In addition to providing filtering, C1 and C2 also affect the turn-on time
of the circuit at power-up, since the two capacitors must charge up through the internal 50K and 125K resistors. The
graph of Figure 1 indicates the turn-on time upon application of VCC of +6V. The turn-on time is ≈ 60% longer for
VCC =3V, and ≈ 20% less for VCC =9V. Turn-off time is <10uS upon removal of VCC.
CHIP DISABLE
The chip Disable (pin 1) can be used to power down the IC to conserve power, or for muting, or both. When at a Logic
“0” (0V to 0.8V), the TS34119 is enabled for normal operation. When pin 1 is a Logic ”1” (2V to VCC), the IC is
disabled. If pin 1 is open, that is equivalent to Logic “0” although good design proactive dictates that an input should
never be left open. Input impedance at pin 1 is a nominal 90K. The power supply current (when disabled) is shown
in Figure 15. Muting, defined as the change in differential gain from normal operation to muted operation, is in excess
of 70dB. The turn-off time the audio output, from the application of the CD signal, is <2uS, and turn on-time is 12 mS-
15mS. Both times are independent of C1, C2, and VCC. When the TS34119 is disabled, the voltage at FC1 and FC2
do not change as they are powered from Vcc. The outputs, VO1 and VO2, change to high impedance condition,
removing the signal from the speaker. If signals from other sources are to be applied to the outputs (while disabled),
they must be within the range of VCC and Ground.
LAYOUT CONSIDERATIONS
Normally a snobbier is not needed at the output of the TS34119, unlike many other audio amplifiers, However, the PC
board layout, stray capacitances, and the manner in which the speaker wires are configured, may dictate otherwise.
Generally, the speaker wires should be twisted tightly, and not more than a few inches in length.
相关PDF资料
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