1

2

3

4

5

6

GAIN/SLV

/FAULT

/OTW_CLIP

GND

GND

VDD

GND

R1

R2

AVDD

TPA3221

8

21

22

IN2_M

IN1

IN2_P

IN1_P

IN1_M

9

+

-

+

-

IN2

16

TPA3221

SLASEE9 – JUNE 2017

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Product Folder Links: TPA3221

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Copyright © 2017, Texas Instruments Incorporated

Feature Description (continued)

In systems with single ended audio inputs the device gain will typically need to be set higher than for systems

with balanced audio input signals.

Figure 5. Single Ended Audio Input Configuration

9.3.2 Gain Setting And Master / Slave Operation

The gain of TPA3221 is set by the voltage divider connected to the GAIN/SLV control pin. Master or Slave mode

is also controlled by the same pin. An internal ADC is used to detect the 8 input states. The first four stages sets

the GAIN in Master mode in gains of 18, 24, 30, 34 dB respectively, while the next four stages sets the GAIN in

Slave mode in gains of 18, 24, 30, 34 dB respectively. The gain setting is latched during power-up and cannot be

changed while device is powered. Table 2 shows the recommended resistor values, the state and gain:

Table 2. Gain and Master / Slave

Master / Slave

mode

Gain

R1 (to GND)

R2 (to AVDD)

Differential input

signal level

(each input pin)

Single Ended input signal level

Master

18 dB

5.6 kΩ

OPEN

2 VRMS

Not reccommended

Master

24 dB

20 kΩ

100 kΩ

1 VRMS

2 VRMS

Master

30 dB

39 kΩ

100 kΩ

0.5 VRMS

1 VRMS

Master

34 dB

47 kΩ

75 kΩ

0.32 VRMS

0.63 VRMS

Slave

18 dB

51 kΩ

51 kΩ

2 VRMS

Not reccommended

Slave

24 dB

75 kΩ

47 kΩ

1 VRMS

2 VRMS

Slave

30 dB

100 kΩ

39 kΩ

0.5 VRMS

1 VRMS

Slave

34 dB

100 kΩ

16 kΩ

0.32 VRMS

0.63 VRMS

Figure 6. Gain and Master / Slave Setup

For easy multi-channel system design TPA3221 has a Master / Slave feature that allows automatic

synchronization of a number of slave devices to be operated at the PWM switching frequency of a master device.

This benefits system noise performance by elliminating spurious cross talk sum and difference tones due to un-

synchronized channel to channel switching frequencies. Furthermore the Master / Slave scheme is designed to

interleave switching of the individual channels in a multi-channel system such that the efficient power supply

current's ripple frequency efficiently is moved to a higher frequency which reduces the RMS ripple current in the

power supply bulk capacitors. The master / Slave scheme and the interleaving of the output stages' switching is

automatically setup by connecting the OSCM of the Master device to the OSCM to a Slave1 device and to OSCP

on a Slave2 device and OSCP on the Master device to the OSCP on a Slave1 device and to OSCM on a Slave2

device. All switching channels are automatically synchronized by releasing /RESET on all devices at the same

time.