DRV612_16 Datasheet, PDF (11/22 Pages) Texas Instruments – 2-Vrms DirectPath Line Driver With Programmable-Fixed Gain

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DRV612
SLOS690B – DECEMBER 2010 – REVISED APRIL 2011
Input-Blocking Capacitors
DC input-blocking capacitors are required to be added in series with the audio signal into the input pins of the
DRV612. These capacitors block the dc portion of the audio source and allow the DRV612 inputs to be properly
biased to provide maximum performance. The input blocking capacitors also limit the dc gain to 1, limiting the
dc-offset voltage at the output.
These capacitors form a high-pass filter with the input resistor, R_IN. The cutoff frequency is calculated using
Equation 1. For this calculation, the capacitance used is the input-blocking capacitor and the resistance is the
input resistor chosen from Table 2. Then the frequency and/or capacitance can be determined when one of the
two values is given.
fc_IN
+
2p
1
R_IN
C_IN
or
C_IN
+
2p
1
fc_IN
R_IN
(1)
For a fixed cutoff frequency of 2 Hz, the size of the input capacitance is shown in Table 2 with the capacitors
rounded up to nearest E6 values. For 20-Hz cutoff, simply divide the capacitor values with 10; e.g., for 1× gain,
150 nF is needed.
Table 2. Input Capacitor for Different Gain and Cutoff
Gain_set
RESISTOR
249 kΩ
82k5
51k1
34k8
27k4
20k5
15k4
11k5
9k09
7k5
6k19
5k11
4k22
GAIN
–2 ×
–1 ×
–1.5×
–2.3×
–2.5×
–3×
–3.5×
–4×
–5×
–5.6×
–6.4×
–8.3×
–10×
Gain
(dB)
6
0.0
3.5
7.2
8
9.5
10.9
12
14
15
16.1
18.4
20
INPUT
RESISTANCE
37 kΩ
55 kΩ
44 kΩ
33 kΩ
31 kΩ
28 kΩ
24 kΩ
22 kΩ
18 kΩ
17 kΩ
15 kΩ
12 kΩ
10 kΩ
2 Hz
Cutoff
2.2 µF
1.5 µF
2.2 µF
3.3 µF
3.3 µF
3.3 µF
3.3 µF
4.7 µF
4.7 µF
4.7 µF
6.8 µF
6.8 µF
10 µF
Pop-Free Power Up
Pop-free power up is ensured by keeping the MUTE pin low during power-supply ramp-up and -down. The pins
should be kept low until the input ac-coupling capacitors are fully charged before asserting the MUTE pin high,
this way proper pre-charge of the ac-coupling is performed and pop-less power up is achieved. Figure 9
illustrates the preferred sequence.
Supply
Supply ramp
MUT_E
Time for ac -coupling
capasitors to charge
Figure 9. Power-Up/Down Sequence
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