Texas Instruments TPA3220, Руководство пользователя

Страница: 13 / 32

6
Ÿ
3 Ÿ
4 Ÿ
2
Ÿ
8 Ÿ
cut off
1 1
50.3 kHz
2 L C 2 10 H 1 F
-
= = =
p ´ p m ´ m
F
www.ti.com
Hardware Configuration
13 SLAU754A – January 2018 – Revised August 2019
Submit Documentation Feedback
Copyright © 2018–2019, Texas Instruments Incorporated
TPA3220 Evaluation Module
3.6.2.3 PVDD (12 V to 30 V) and 5-V Supply
This power mode is most useful for systems in which a 5-V supply is already available due to additional
circuitry like an MCU or wireless module. On the EVM, this is also the preferred way to measure efficiency
of the TPA3220 device. The PVDD voltage can still be connected to J1 but jumpers J29 and J24 must be
removed. The 5-V supply should be connected to TP33 (5V-PU) or TP34 (5V-EXT).
If R3 is installed, these nodes will be connected and at the same voltage. The same 5-V input will be used
for the TPA3220 supplies (AVDD, VDD, and GVDD), the EVM reset control (U7), all TPA3220 device
pullups (Reset, HEAD, FREQ_ADJ, Fault, OTW_CLIP), and status LEDs D4 and D2.
The two 5-V supplies can be isolated by removing R3. Once R3 is removed, 5 V can be fed to only the
TPA3220 supplies through TP34 (5V-EXT) and all other 5 V needs can be powered through TP33 (5V-
PU).
Either approach can be used to measure efficiency, but the most accurate numbers will be with the two 5-
V supplies separated so the TPA3220 supply voltage is isolated and measured independently of board
LEDs, reset control, and so forth.
3.7 LC Response and Overview
Included near the output of the TPA3220 device are four output LC filters. These output filters filter the
PWM output leaving only the audio content at high power which is fed to the speakers. The board uses a
Sagami
®
10-µH inductor and 1-µF film capacitor to form this LC filter. Using the equations listed in LC
Filter Design , the filter low pass cut-off is as follows:
(1)
The frequency response of the filter per output load is illustrated in Figure 6 .
Figure 6. Filter Frequency Response
Figure 6 is taken directly from the LC Filter Calculator tool available on TI.com ( SLAC729 ). The tool is
configured for BTL common mode with values of 10 µH and 1 µF for the filter. This tool is also helpful
when designing a different board featuring one of TI’s class-D amplifiers.