DRV632 Datasheet, PDF (10/23 Pages) Texas Instruments – DirectPath™, 2-VRMS Audio Line Driver With Adjustable Gain

DRV632
SLOS681B – JANUARY 2011 – REVISED AUGUST 2015
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Feature Description (continued)
9.3.3 Decoupling Capacitors
The DRV632 is a DirectPath line-driver amplifier that requires adequate power supply decoupling to ensure that
the noise and total harmonic distortion (THD) are low. A good, low equivalent-series-resistance (ESR) ceramic
capacitor, typically 1 μF, placed as close as possible to the device VDD lead works best. Placing this decoupling
capacitor close to the DRV632 is important for the performance of the amplifier. For filtering lower-frequency
noise signals, a 10-μF or greater capacitor placed near the audio power amplifier would also help, but it is not
required in most applications because of the high PSRR of this device.
9.3.4 Gain-Setting Resistor Ranges
The gain-setting resistors, R_IN and R_fb, must be chosen so that noise, stability, and input capacitor size of the
DRV632 are kept within acceptable limits. Voltage gain is defined as R_fb divided by R_IN.
Selecting values that are too low demands a large input ac-coupling capacitor, C_IN. Selecting values that are too
high increases the noise of the amplifier. Table 1 lists the recommended resistor values for different inverting-
input gain settings.
GAIN
–1 V/V
–1.5 V/V
–2 V/V
–10 V/V
Table 1. Recommended Resistor Values
INPUT RESISTOR VALUE, R_IN
10 kΩ
8.2 kΩ
15 kΩ
4.7 kΩ
FEEDBACK RESISTOR VALUE, R_fb
10 kΩ
12 kΩ
30 kΩ
47 kΩ
9.3.5 Input-Blocking Capacitors
DC input-blocking capacitors are required to be added in series with the audio signal into the input pins of the
DRV632. These capacitors block the dc portion of the audio source and allow the DRV632 inputs to be properly
biased to provide maximum performance.
These capacitors form a high-pass filter with the input resistor, R_IN. The cutoff frequency is calculated using
Equation 3. For this calculation, the capacitance used is the input-blocking capacitor, and the resistance is the
input resistor chosen from Table 1; then the frequency and/or capacitance can be determined when one of the
two values is given.
It is recommended to use electrolytic capacitors or high-voltage-rated capacitors as input blocking capacitors to
ensure minimal variation in capacitance with input voltages. Such variation in capacitance with input voltages is
commonly seen in ceramic capacitors and can increase low-frequency audio distortion.
1
1
f_cIN = _{2p RINCIN}
or
C_IN = _{2p fcINRIN}
(3)
9.3.6 DRV632 UVP Operation
The shutdown threshold at the UVP pin is 1.25 V. The customer must use a resistor divider to obtain the
shutdown threshold and hysteresis desired for a particular application. The customer-selected thresholds can be
determined as follows:
9.3.7 External Undervoltage Detection
External undervoltage detection can be used to mute/shut down the DRV632 before an input device can
generate a pop.
The shutdown threshold at the UVP pin is 1.25 V. The user selects a resistor divider to obtain the shutdown
threshold and hysteresis for the specific application. The thresholds can be determined as follows:
V_UVP = (1.25 – 6 μA × R3) × (R1 + R2) / R2
Hysteresis = 5 μA × R3 × (R1 + R2) / R2
For example, to obtain V_UVP = 3.8 V and 1-V hysteresis, use R1 = 3 kΩ, R2 = 1 kΩ, and R3 = 50 kΩ.
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