cIN

IN

IN

IN

cIN

IN

1

1

f

=

C

=

2 R

C

2 f

R

or

p

p

10

DRV632

SLOS681C – JANUARY 2011 – REVISED AUGUST 2019

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Copyright © 2011–2019, Texas Instruments Incorporated

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, RIN and Rfb, must be chosen so that noise, stability, and input capacitor size of the

DRV632 are kept within acceptable limits. Voltage gain is defined as Rfb divided by RIN.

Selecting values that are too low demands a large input ac-coupling capacitor, CIN. 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.

Table 1. Recommended Resistor Values

GAIN

INPUT RESISTOR VALUE, RIN

FEEDBACK RESISTOR VALUE, Rfb

–1 V/V

10 k

Ω

10 k

Ω

–1.5 V/V

8.2 k

Ω

12 k

Ω

–2 V/V

15 k

Ω

30 k

Ω

–10 V/V

4.7 k

Ω

47 k

Ω

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, RIN. 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.

(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:

VUVP = (1.25 – 6 μA × R3) × (R1 + R2) / R2

Hysteresis = 5 μA × R3 × (R1 + R2) / R2

For example, to obtain VUVP = 3.8 V and 1-V hysteresis, use R1 = 3 kΩ, R2 = 1 kΩ, and R3 = 50 kΩ.