TPA3255EVM

TPA3255EVM

Trademarks

PurePath is a trademark of Texas Instruments.

1 Hardware Overview

The TPA3255EVM PurePath™ Ultra-HD evaluation module demonstrates the TPA3255DDV integrated circuit from Texas Instruments. The TPA3255DDV is a high-performance high-power class-D amplifier that enables true premium sound quality with high-efficiency class-D technology. It features an advance integrated feedback design and high-speed gate driver error correction (PurePath Ultra-HD), which enables ultra-low distortion across the audio band and superior audio quality. This EVM supports two BTL (stereo 2.0) output channels, one PBTL (mono 0.1) output channel, one BTL plus two SE (2.1) output channels, and four SE (4.0) output channels configurations. The NE5532 is a High Performance Audio Op Amp designed to allow TPA3255DDV operation with differential or single ended input signals to the EVM with differential inputs yielding the optimal performance. TPA3255EVM is a complete 2-Vrms analog input 2 × 315-W stereo/1 × 600-W mono high-power amplifier ready for evaluation and excellent listening experience.

Figure 1. TPA3255EVM

1.1 TPA3255EVM Features

The TPA3255EVM has the following features:

• Stereo PurePath Ultra-HD evaluation module
• Self-contained protection system (short circuit, clip, and thermal)
• Standard 4-V_RMS differential input or single-ended line input
• BTL, PBTL, and SE output configuration support
• Frequency adjust and oscillator sync interface
• Single supply voltage range 14–53.5 V
• Double-sided, plated-through, 2-oz. Cu 2-layer PCB layout

1.2 TPA3255EVM Frequency Adjust

The TPA3255EVM offers hardware trimmed oscillator frequency by external control of the FREQ_ADJ pin. The Frequency adjust can be used to reduce interference problems while using a radio receiver tuned within the AM band, the switching frequency can be changed from nominal to lower values. These values should be chosen such that the nominal and the lower value switching frequencies together results in the fewest cases of interference throughout the AM band. The oscillator frequency can be selected by the value of the FREQ_ADJ resistor connected to GND in master mode according to Table 1.

For slave-mode operation, turn off the oscillator by pulling the FREQ_ADJ pin to DVDD. This configures the OSC_I/O pins as inputs to be slaved from an external differential clock. In a master/slave system inter-channel delay is automatically set up between the switching phases of the audio channels, which can be illustrated by no idle channels switching at the same time. This will not influence the audio output, but only the switch timing to minimize noise coupling between audio channels through the power supply. This will optimize audio performance and result in better operating conditions for the power supply. The inter-channel delay will be set up for a slave device depending on the polarity of the OSC_I/O connection such that slave mode 1 is selected by connecting the OSC_I/O of the master device with the OSC_I/O of the slave device with the same polarity (+ to + and – to –), while slave mode 2 is selected by connecting the OSC_I/O's with the inverse polarity (+ to – and – to +).

1.3 TPA3255EVM Single-Ended and Differential Input

The TPA3255EVM supports both differential and single-ended inputs. For single-ended inputs, J4 and/or J19 jumpers are set to the SE position, so that the TPA3255EVM uses the NE5532 to convert the single-ended input signal to differential to properly drive the differential inputs of the TPA3255. The input RCA jack, J3, is used to provide INA inputs and RCA jack J14 is used to provide INB inputs. RCA jack J18 is used to provide INC inputs and RCA jack J15 is used to provide IND inputs with differential inputs.

For differential input operation, J4 and/or J19 jumpers are set to the DIFF position, and the TPA3255EVM uses the NE5532 to buffer the differential input signal to the differential inputs of the TPA3255. The input RCA jack, J3, is used to provide INA, RCA jack J14 provides INB, RCA jack J18 provides INC, and RCA jack J15 provides IND with differential inputs.