Texas Instruments TPA31 D2 Series, Руководство пользователя, Страница: 14 / 48

i i
1
f
2 Z C
p
=
ƒ
5
6
7
8
9
10
INNR
PLIMIT
GVDD
GAIN/SLV
GND
2 1
1
2 C5 1 F µ
2 1
51 k R1
51 k R2
14
TPA3116D2, TPA3118D2, TPA3130D2
SLOS708G – APRIL 2012 – REVISED DECEMBER 2017 www.ti.com
Product Folder Links: TPA3116D2 TPA3118D2 TPA3130D2
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Copyright © 2012–2017, Texas Instruments Incorporated
Feature Description (continued)
(1) Resistor tolerance should be 5% or better.
Table 1. Gain and Master/Slave
MASTER / SLAVE
MODE
GAIN R1 (to GND)
(1)
R2 (to GVDD)
(1)
INPUT IMPEDANCE
Master 20 dB 5.6 k Ω OPEN 60 k Ω
Master 26 dB 20 k
Ω
100 k
Ω
30 k
Ω
Master 32 dB 39 k Ω 100 k Ω 15 k Ω
Master 36 dB 47 k Ω 75 k Ω 9 k Ω
Slave 20 dB 51 k Ω 51 k Ω 60 k Ω
Slave 26 dB 75 k Ω 47 k Ω 30 k Ω
Slave 32 dB 100 k
Ω
39 k
Ω
15 k
Ω
Slave 36 dB 100 k Ω 16 k Ω 9 k Ω
Figure 27. Gain, Master/Slave
In Master mode, SYNC terminal is an output, in Slave mode, SYNC terminal is an input for a clock input. TTL
logic levels with compliance to GVDD.
7.3.2 Input Impedance
The TPA31xxD2 family input stage is a fully differential input stage and the input impedance changes with the
gain setting from 9 k
Ω at 36 dB gain to 60 k Ω at 20 dB gain. Table 1 lists the values from min to max gain. The
tolerance of the input resistor value is ±20% so the minimum value will be higher than 7.2 k Ω . The inputs need to
be AC-coupled to minimize the output dc-offset and ensure correct ramping of the output voltages during power-
ON and power-OFF. The input ac-coupling capacitor together with the input impedance forms a high-pass filter
with the following cut-off frequency:
(1)
If a flat bass response is required down to 20 Hz the recommended cut-off frequency is a tenth of that, 2 Hz.
Table 2 lists the recommended ac-couplings capacitors for each gain step. If a -3 dB is accepted at 20 Hz 10
times lower capacitors can used – for example, a 1 µF can be used.
Table 2. Recommended Input AC-Coupling Capacitors
GAIN INPUT IMPEDANCE INPUT CAPACITANCE HIGH-PASS FILTER
20 dB 60 k
Ω
1.5 µF 1.8 Hz
26 dB 30 k Ω 3.3 µF 1.6 Hz
32 dB 15 k Ω 5.6 µF 1.9 Hz
36 dB 9 k Ω 10 µF 1.8 Hz