This User’s Guide describes the operation of the evaluation module (TPA3255EVM, rev A) for the
TPA3255 315-W Stereo/600-W mono PurePath™ Ultra-HD Analog Input Power Stage. The user’s guide
also provides design information, which includes schematics, BOM, and PCB layout. For questions and
support go to the E2E forums (e2e.ti.com).
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.
Hardware Overview
2.1TPA3255EVM 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
•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
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.
Table 1. Frequency Adjust Master Mode Selection
Master ModeResistor to GND
Nominal30 kΩ
AM120 kΩ
AM210 kΩ
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 interchannel 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 interchannel 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 +).
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2.3TPA3255EVM 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 singleended 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.
NOTE: Single-ended input settings on the TPA3255EVM should only be used for channels with
output configuration BTL or PBTL, not SE. For SE output configuration J4 and/or J19
jumpers for that channel must be set to the DIFF position, so the input signal INx is mapped
directly to OUTx.
2.4TPA3255EVM Clip Overtemperature and Fault Indicators
The TPA3255EVM is equipped with LED indicators that illuminate when the FAULT and/or CLIP_OTW pin
goes low. See Table 2 and (SLASEA8) for more details.
Table 2. Fault and Clip Overtemperature Status
FAULTCLIP_OTWDescription
00
00
01Overload (OLP) or undervoltage (UVP). Junction temperature lower than 125°C.
10Junction temperature higher than 125°C (overtemperature warning)
11Junction temperature lower than 125°C and no OLP or UVP faults (normal operation)
Overtemperature (OTE) or overload (OLP) or undervoltage (UVP). Junction temperature higher
than 125°C (overtemperature warning).
Overload (OLP) or undervoltage (UVP). Junction temperature higher than 125°C (overtemperature
warning).
•Check that jumpers are in their default state as shown in Figure 1 and Table 3 for stereo BTL
operation:
Table 3. Stereo BTL Default Jumper States
JumperSettingComment
J29INPVDD to 15-V BUCK
J31IN12-V LDO to 12-V TERM
J32IN3.3-V LDO to 3.3-V TERM
J33IN3.3-V LDO to 3.3-V TERM
J21INCSTART SE
J163 to 4MASTER MODE
J52 to 3M1 – BTL
J62 to 3M2 – BTL
J22INOUTA CAP SHUNT
J23INOUTB CAP SHUNT
J24INOUTC CAP SHUNT
J25INOUTD CAP SHUNT
J262 to 3INC SELECT
J272 to 3IND SELECT
J7OUTPBTL SELECT INC
J8OUTPBTL SELECT IND
J10OUTINC/D DIFF INPUT
J12OUTINC/D DIFF INPUT
J41 to 2INA/B SE INPUT
J191 to 2INC/D SE INPUT
TPA3255EVM Setup
•Set S1 to the RESET position.
•Set power supply to 51 V (14–53.5-V range) and current to 10 A (5–14-A range). Do not power up until
all connections are completed.
•Connect power supply to TPA3255 EVM positive terminal to PVDD (RED) and negative terminal to
GND (BLACK).
•Connect left channel speaker/power resistor load (4–8 Ω) to TPA3255 EVM positive output terminal to
OUTA (RED) and AP analog input channel A positive terminal.
•Connect left channel speaker/power resistor load (4–8 Ω) to TPA3255 EVM negative output terminal to
OUTB (BLACK) and AP analog input channel A negative terminal.
•Connect right channel speaker/power resistor load (4–8 Ω) to TPA3255 EVM positive output terminal
to OUTC (RED) and AP analog input channel B positive terminal.
•Connect right channel speaker/power resistor load (4–8 Ω) to TPA3255 EVM negative output terminal
to OUTD (BLACK) and AP analog input channel B negative terminal.
•Be careful not to mix up PVDD, OUTA, and OUTB terminals, since the colors are the same (RED).
•For single-ended stereo inputs, connect AP channel A XLR to RCA male jacks to female RCA jacks
input A/AB (RED) and AP channel B XLR to RCA male jacks to female RCA jacks input C/CD (WHITE)
and set J4 and J19 jumper positions to SE.
•For differential stereo inputs, connect positive RCA male jacks to female RCA jacks input A/AB
(RED) and input C/CD (WHITE) and connect negative RCA male jacks to female RCA jacks input B
(BLUE) and input D (BLACK) and set J4 and J19 jumper positions to DIFF.
•Power up power supply once all the connections are made correctly and the 3.3-V and12-V LEDs
(GREEN) will illuminate.
•CLIP_OTWz (ORANGE) and FAULTz (RED) LEDs should be off, if the audio source is off.
NOTE: J3/J10 and J18/J15 can be used for differential inputs to INA/INB and INC/IND, respectively.
Using a smart phone, tablet, or PC with headphone to RCA cable, audio streaming via headphone jack
can begin once the EVM is powered up correctly with jumpers in their default state. Start the media player
of your choice and enjoy the enhanced audio performance TPA3255 provides as a quick check of the
setup.
Using TPA3255EVM in Different Output Configurations
4Using TPA3255EVM in Different Output Configurations
The TPA3255EVM can be configured for four different output operations. The 2.0 BTL configuration is the
default set up of the TPA3255EVM described in Section 3.3. The remaining three configurations are 2.1
BTL plus two single-ended (SE) outputs, 0.1 PBTL output, and 4.0 single-ended (SE) outputs.
Using TPA3255EVM in Different Output Configurations
•Connect right (stereo) channel input to female RCA jack input D (BLACK) for OUTD speaker.
•For single-ended subwoofer (mono) input, connect RCA male jack to female RCA jack input A/AB
(RED) and set J4 jumper positions to SE.
•For differential subwoofer (mono) inputs, connect positive RCA male jack to female RCA jack input
A/AB (RED) and connect negative RCA male jack to female RCA jack input B (YELLOW) and set J4
jumper positions to DIFF.
NOTE: OUTC and OUTD are the single-ended output channels and OUTA and OUTB are the BTL
channel for 2.1 operations.
4.2PBTL (0.1) Output Operation
Configure the EVM as follows for PBTL operations:
Table 6. PBTL Default Jumper States
JumperSettingComment
J29INPVDD to 15-V BUCK
J31IN12-V LDO to 12-V TERM
J32IN3.3-V LDO to 3.3-V TERM
J33IN3.3-V LDO to 3.3-V TERM
J21INCSTART SE
J163 to 4MASTER MODE
J52 to 3M1 – PBTL
J61 to 2M2 – PBTL
J22INOUTA CAP SHUNT
J23INOUTB CAP SHUNT
J24INOUTC CAP SHUNT
J25INOUTD CAP SHUNT
J262 to 3INC SELECT
J272 to 3IND SELECT
J72 to 3PBTL SELECT INC – GND
J82 to 3PBTL SELECT IND – GND
J10OUTINC/D DIFF INPUT
J12OUTINC/D DIFF INPUT
J41 to 2INA/B SE INPUT
J191 to 2INC/D SE INPUT
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•Set J6 to H and J5 to L.
•Connect speaker/power resistor (2–4 Ω) positive terminal to OUTA and OUTC (OUT A and C shorted).
•Connect speaker/power resistor (2–4 Ω) negative terminal to OUTB and OUTD (OUT B and D
shorted).
•Install PBTL jumpers J7 and J8 (pulls input C and input D to GND).
•For single-ended mono input, connect RCA male jack to female RCA jack input A/AB (RED) and set
J4 jumper positions to SE.
•For differential mono inputs, connect positive RCA male jack to female RCA jack input A/AB (RED)
and connect negative RCA male jack to female RCA jack input B (YELLOW) and set J4 jumper
position to DIFF.
NOTE: INA and INB are the inputs for PBTL and INC and IND are grounded for PBTL operation.
Configure the EVM as follows for 4 single-ended operations:
Table 7. SE 4.0 Default Jumper States
JumperSettingComment
J29INPVDD to 15-V BUCK
J31IN12-V LDO to 12-V TERM
J32IN3.3-V LDO to 3.3-V TERM
J33IN3.3-V LDO to 3.3-V TERM
J21INCSTART SE
J163 to 4MASTER MODE
J51 to 2M1 – 4XSE
J61 to 2M2 – 4XSE
J22OUTOUTA CAP SHUNT
J23OUTOUTB CAP SHUNT
J24OUTOUTC CAP SHUNT
J25OUTOUTD CAP SHUNT
J262 to 3INC SELECT
J272 to 3IND SELECT
J7OUTPBTL SELECT INC
J8OUTPBTL SELECT IND
J10OUTINC/D DIFF INPUT
J12OUTINC/D DIFF INPUT
J42 to 3INA/B DIFF INPUT
J192 to 3INC/D DIFF INPUT
Using TPA3255EVM in Different Output Configurations
•Set J6 to H and J5 to H.
•Connect speaker/power resistor (2–4 Ω) positive terminal to OUTA and remove jumper J22.
•Connect speaker/power resistor (2–4 Ω) positive terminal to OUTB and remove jumper J23.
•Connect speaker/power resistor (2–4 Ω) positive terminal to OUTC and remove jumper J24.
•Connect speaker/power resistor (2–4 Ω) positive terminal to OUTD and remove jumper J25.
•Set both J4 and J19 jumpers position to DIFF.
•Connect input to female RCA jack input A/AB (RED) for OUTA speaker.
•Connect input to female RCA jack input B (YELLOW) for OUTB speaker.
•Connect input to female RCA jack input C/CD (WHITE) for OUTC speaker.
•Connect input to female RCA jack input D (BLACK) for OUTD speaker.
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NOTE: The performance of the TPA3255EVM/TPA3255DDV is dependent on the power supply.
Design the power supply with margins that can deliver the needed power. In low-frequency
applications additional bulk capacitance may be needed. Replacing the bulk capacitors on
the TPA3255EVM with more capacitance may be necessary, depending on the power supply
used.
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