TPA6204A1_17 Datasheet, PDF (14/26 Pages) Texas Instruments – 1.7-W Mono Fully Differential Audio Power Amplifier

TPA6204A1
SLOS429C – MAY 2004 – REVISED MAY 2016
www.ti.com
The internal feedback resistors (RF) are trimmed to 40 kΩ. Resistor matching is very important in fully differential
amplifiers. The balance of the output on the reference voltage depends on matched ratios of the resistors.
CMRR, PSRR, and the cancellation of the second harmonic distortion diminishes if resistor mismatch occurs.
Therefore, TI recommends using 1% tolerance resistors or better to keep the performance optimized.
10.2.2.2 Using Low-ESR Capacitors
Low-ESR capacitors are recommended throughout this applications section. A real (as opposed to ideal)
capacitor can be modeled simply as a resistor in series with an ideal capacitor. The voltage drop across this
resistor minimizes the beneficial effects of the capacitor in the circuit. The lower the equivalent value of this
resistance the more the real capacitor behaves like an ideal capacitor.
10.2.2.2.1 Bypass Capacitor (C_(BYPASS)) and Start-Up Time
The internal voltage divider at the BYPASS pin of this device sets a mid-supply voltage for internal references
and sets the output common-mode voltage to VDD/2. Adding a capacitor to this pin filters any noise into this pin
and increases kSVR. C_(BYPASS) also determines the rise time of VO+ and VO− when the device is taken out of
shutdown. The larger the capacitor, the slower the rise time. Figure 10 shows the relationship of C_(BYPASS) to
start-up time.
10.2.2.2.2 Input Capacitor (C_I)
The TPA6204A1 does not require input coupling capacitors if using a differential input source that is biased from
0.5 V to VDD − 0.8 V. Use 1% tolerance or better gain-setting resistors if not using input coupling capacitors. In
the single-ended input application an input capacitor, CI, is required to allow the amplifier to bias the input signal
to the proper DC level. In this case, CI and RI form a high-pass filter with the corner frequency determined in
Equation 9.
f_c
=
1
2pR_IC_I
(9)
−3 dB
f_c
Figure 17. CI and RI High-Pass Filter Cutoff Frequency
The value of CI is important to consider as it directly affects the bass (low frequency) performance of the circuit.
Consider the example where RI is 10 kΩ and the specification calls for a flat bass response down to 100 Hz.
Equation 9 is reconfigured as Equation 10.
C_I
=
1
2pR_I f_c
(10)
In this example, CI is 0.16 μF, so one would likely choose a value in the range of 0.22 μF to 0.47 μF. Ceramic
capacitors should be used when possible, as they are the best choice in preventing leakage current. When
polarized capacitors are used, the positive side of the capacitor must face the amplifier input in most applications,
as the DC level there is held at VDD/2, which is likely higher than the source DC level. It is important to confirm
the capacitor polarity in the application.
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